Tampere University: TAU

Tampere University / Computational Physics: Computational Physics (Electronic Structure Theory)

Home page: Associate Professor Eero Arola

Dr. Tech., Docent (Associate Professor) in Solid State Physics [theory]

Unit of Physics

Faculty of Engineering and Natural Sciences

Tampere University / Hervanta Campus

Korkeakoulunkatu 3

33720 Tampere

Finland

Telephone switchboard: +358 (0) 294 5211

E-mail: eero.arola@tuni.fi / earola7@gmail.com

URL: homepages.tuni.fi/eero.arola

About

Eero Arola received the Dipl. Eng. (M.Sc.Tech.) degree from the Department of Physics at Tampere University of Technology (TUT), Finland in 1982 in theoretical and computational physics and electrical engineering, and the Dr. Tech. (Ph.D.) degree from the Department of Physics at TUT, in 1991 in theoretical and computational solid state physics.

His M.Sc. thesis, entitled “Calculation of Electron States in Solids by Augmented-Plane-Wave Method (APW)” (transl. from Finnish), was supervised by Prof. Markus Pessa at TUT. His Ph.D. dissertation, entitled “The Relativistic KKR-CPA Method: A Study of Electronic Structures of Cu₇₅Au₂₅, Au₇₀Pd₃₀, and Cu₇₅Pt₂₅ Disordered Alloys”, was supervised by Prof. Arun Bansil (University Distinguished Professor) from Northeastern University, Boston, Massachusetts, USA and Dr. Rajanikanth S. Rao from the National Physical Laboratory, Delhi, India. Professor Balázs L. Győrffy (see also: https://en.wikipedia.org/wiki/Balázs_Győrffy) from the University of Bristol (UK) acted as an external examiner of the doctoral dissertation and the opponent in its public defense on the 8^th of March, 1991. Dr. Arola’s dissertation received those days rarely admitted grade of “passed with commendation” (excellent) from its external examiners Prof. Juhani von Boehm (Helsinki University of Technology, nowadays Aalto University) and Prof. Balazs L. Gyorffy (University of Bristol, UK).

One of the best memorial photos from Eero Arola’s doctoral celebration party (traditionally called “Karonkka”) can be seen here: photo_Doctoral_Karonkka_Eero_Arola_March_8_1991 (from the left: Prof. Markus Pessa, Prof. Balazs Gyorffy, Mr. (Dr.Tech.) Eero Arola and Prof. Arun Bansil).

Between 1992-2001 he has been working as a Post-Doctoral Research Fellow in several internationally recognized theoretical condensed matter physics research groups at the University of Bristol (UK) with Balázs L. Győrffy (see also: https://en.wikipedia.org/wiki/Balázs_Győrffy), at the Keele University (UK) with Prof. Paul Strange (nowadays Emeritus Professor of Theoretical Physics at University of Kent) and at the University of Bath (UK) with Dr Simon Crampin under the auspices of the Academy of Finland and the Royal Society of the UK (Bristol) and the Engineering and Physical Sciences Research Council (EPSRC) of the UK (Keele and Bath).

In 2002 he returned back to TUT to work as a Senior Researcher in the Optoelectronics Research Centre (ORC) and Institute of Physics at TUT with Prof. Tapio Rantala, the leader of the Semiconductor Physics Laboratory (nowadays Emeritus Professor of Physics at Tampere University).

His recent research interests have been in first-principles theories and calculations on electronic, optical and dielectric properties of semiconductors and polymers, and the application of nonlinear quantum mechanical perturbation theory to calculate laser-pulse-induced electric breakdown (ablation) in dielectric materials. His major research activities in the past have included theoretical studies on developing and implementing first-principles fully relativistic and magnetic x-ray diffraction (RMXRD) theories for magnetic metals and alloys based on the quantum field theory and developing a fully relativistic magnetic second harmonic generation (RMSHG) theory for magnetic layered materials. He has some 25 years of experience on these issues. Most recently Dr. Arola acted as a project manager in ORC and Department of Physics at TUT within the Tekes-funded NANOPOWER and NANOCOM consortium research projects, respectively which aimed to develop novel polymer nanocomposites for high-voltage power capacitors.

Since 2007 Dr. Arola has hold a few academia related positions of trust. Namely, he has been a member and vice-chairman of the Tampere Society for Associate Professors board, member of the Finnish Union of Docents board and more recently has become a board member of the 3T Association of Finnish Union of Researchers and Teachers.

Dr. Arola has in 2019 accomplished a professional teaching pedagogical qualification international programme (60 ECTS credits) at Tampere University of Applied Sciences (TAMK). Consequently, Dr. Arola has become interested in designing, developing and implementing teaching videos and online-courses in mathematics, theoretical physics and engineering topics where Phenomenon and Problem Based Learning methods are exploited with an additional flavour of his unique guitar music outdoor performances by the beautiful Finnish lakeside. That is just great fun to activate online-students’ learning process more effective!

Dr. Arola is a member of the Finnish Physical Society and among the 65 recipients of the Institute of Physics (IOP, UK) Outstanding Reviewer Awards 2022 for the Journal of Physics: Condensed Matter (IOP Awards 2022 news).

Employment History

The Academic Employment Portfolio of Assoc. Prof. Eero Arola briefly describes his most important research posts in England during 1992–2001 and research and teaching posts and contracts he had during 1978–1992 and 2002–2014 at Tampere University of Technology (TUT) in Finland. Because the majority of his large number of research and teaching posts and contracts at TUT are part-time and temporary contracts the consecutive contracts under the same teaching or research topic have been grouped into one employment record. For further details of these posts and contracts, see Dr. Arola’s Service Record (in Finnish).

Since August 2021, after his retirement from the TUT, Dr. Arola has started to teach mathematics, physics and chemistry at many primary, secondary and high schools ran by the City of Tampere. At present, Dr. Arola is acting as a mathematics and physics teacher at Tampere Vocational College Tredu.

Teaching Experience and Qualifications

Assoc. Prof. Arola has a long-term teaching history within the Department of Physics at the Tampere University of Technology during 1978 – 2009, apart from his post-doctoral research posts in England during 1992 – 2001 and teaching pedagogical postgraduate studies at Keele University during 2001 – 2002. In the past he has carried out teaching physics in all traditional university teaching forms: running theoretical and laboratory exercises as well as lecturing. In particular, he has a long experience of running theoretical exercises (problem-solving classes) and lecturing theoretical topics of physics in courses at undergraduate to postgraduate level.

Recently Dr. Arola has completed his postgraduate studies in the Professional Teacher Education programme 17ETaTo for pedagogical teaching qualification (60 ECTS) at Tampere University of Applied Sciences (TAMK) and graduated on 18 December 2019. The highlights and details of his learning process during the 17ETaTo Programme can be seen in his Learning Diary (Learning Journal) and the Development Project Report whose title was “Improving Mathematics Learning of Undergraduate and High School Students through Phenomenon and Problem Based Learning Methods” (Arola, 2019, 57 pages).

For further details about Dr. Arola’s teaching, supervision and pedagogical teaching qualifications and philosophy, see his Teaching Portfolio.

Research Experience in General

Dr. Arola’s main research interest is centered on theoretical, computational and to some extent mathematical physics and to apply these for a variety of novel problems occurring in physical sciences, materials science and engineering. He has some 25 years of experience on these issues, in particular to those formulated within the relativistic quantum mechanics. Some examples of his past and present research topics within these categories are briefly described below. Moreover, due to Dr. Arola’s long-term research experience as a post-doctoral research fellow in three internationally leading theoretical materials physics groups in England (University of Bristol, Keele University and University of Bath) I have divided my research experience into Finnish and British categories below.

Research Experience in Finland

Nostalgic studies: M.Sc. thesis and Pre-M.Sc. research report: Implementation and application of the nonrelativistic APW electronic structure method for metals

Assoc. Prof. Eero Arola’s first nostalgic touching point to develop, implement and apply quantum mechanical methods for theoretical and computational materials science research was when he chose the research topic for his M.Sc. thesis titled “Kiinteän aineen elektronitilojen laskeminen Augmented Plane Wave –menetelmällä” (“Calculation of Electron States in Solids by Augmented-Plane-Wave Method”) in the framework of the density functional theory (DFT).

Professor Markus Pessa, his thesis supervisor from the Department of Physics, TUT, was an experimentalist and therefore Mr Arola in the early 1980s had to carry out this theoretical and computational project, including the scientific program coding stages, virtually on his own, very independently. Mr Arola then demonstrated that his simple featured (no charge- and spin-self-consistency implemented) electronic structure code could reproduce with an excellent agreement the electronic band structure of the fcc copper (Cu) crystal first published by Glenn A. Burdick (Phys. Rev. vol. 129, p. 138, 1963) by using exactly the same methodology. The M.Sc. thesis of Mr Arola (in Finnish) can be seen here: MSc_thesis_Arola_1982.

After Mr Arola implemented the APW-DFT method he also carried out electronic band structure calculations on the non-magnetic phase of bcc chromium (Cr). Once again, the agreement with previously published electronic band structure results on Cr was very good. These computational results have been published in Mr Arola’s Pre-M-Sc. research report (special assignment in physics, TUT, 1982) titled “Epärelativistisen APW-menetelmän soveltaminen paramagneettisen kromin elektronisten enegiavöiden laskemiseen” (“Application of the nonrelativistic APW-method in calculating electronic energy bands of paramagnetic chromium”). This research report (in Finnish) can be seen here: Pre_MSc_Research_Report_Arola_1982.

Ph.D. dissertation: First-principles relativistic electronic structure methods for metals and alloys

As his PhD project Mr Arola formulated and implemented, first such studies in Finland, the first principles fully relativistic Korringa - Kohn - Rostoker coherent - potential – approximation (R-KKR-CPA) approach in the framework of the density functional theory (DFT) and Green’s function multiple scattering theory. He then applied this theory for computation of the electronic structures of substitutionally disordered random binary alloys containing heavy elements in his Ph.D. dissertation and the three peer-reviewed articles:

1. E. Arola, R. S. Rao, A. Salokatve, and A. Bansil, “Electronic structure of Cu₇₅Au₂₅ disordered alloy”, Physical Review B vol. 41, pp. 7361–7369 (1990).

2. E. Arola, C. J. Barnes, R. S. Rao, and A. Bansil, “Electronic structure of Au₇₀Pd₃₀ disordered alloy”, Physical Review B vol. 42, pp. 8820–8826 (1990).

3. E. Arola, C. J. Barnes, R. S. Rao, A. Bansil, and M. Pessa, “Electronic structure of a Cu₇₅Pt₂₅ disordered alloy”, Surface Science vol. 249, pp. 281–288 (1991).

First-principles computational studies on electronic and atomic structures and defects in GaAs_1-xN_x and GaN_1-yAs_y Alloys and Arsenic Impurities in GaN

[Carried out as part-time research in the Academy of Finland Project 2004–2006: “First-Principles Theory of Optical Properties of New Compound Semiconductor Materials”]

It is well known that linear and nonlinear optical properties such as light absorption, emission and scattering in optoelectronic and photonic devices depend in a complex manner on the underlying electronic, atomic and magnetic structures of these semiconductor devices. Bearing this in mind we have carried out computational studies on electronic and atomic structures, and neutral N interstitial defects in GaAsN (with Prof. Tapio Rantala), as well as neutral and charged substitutional defects in GaAsN alloys and GaN compound (with Prof. Tapio Rantala, Tampere University of Technology and Prof. Risto Nieminen, Helsinki University of Technology), using first-principles density functional theory (DFT) methods.

In connection with this research project Assoc. Prof. Eero Arola has acted as the second supervisor of the PhD student Hannu-Pekka Komsa, the first supervisor being Prof. Tapio Rantala.

Among our research publications on this topic could be mentioned the following ones:

· Paper: E. Arola, J. Ojanen, H.-P. Komsa, and T. T. Rantala, “Atomic and Electronic Structures of N Interstitials in GaAs”, Phys. Rev. B vol. 72, p. 045222: 1–9 (2005).

· Paper: K. Laaksonen, H.-P. Komsa, E. Arola, T. T. Rantala, and R. M. Nieminen, “Computational Study of GaAs_1-xN_x and GaN_1-yAs_y Alloys and Arsenic Impurities in GaN”, J. Phys.: Condens. Matter vol. 18, pp. 10097–10114 (2006).

· Talk: Hannu-Pekka Komsa, Jussi-Ojanen, Eero Arola, and Tapio Rantala, “First-Principles Electronic Structure Studies on Nitrogen Interstitials in GaAs”. Presented in the XXXIX Annual Conference of the Finnish Physical Society, March 17–19, 2005, Espoo, Finland. See this talk here: talk_N_interstitials_in_GaAs.

· Talk: K. Laaksonen, H.-P. Komsa, E. Arola, T. T. Rantala, and R. M. Nieminen, “Electronic and Structural Properties of GaAsN Alloys and Arsenic Impurities in GaN”. Presented in the XL Annual Conference of the Finnish Physical Society, March 9–11, 2006, Tampere, Finland. See this talk here: talk_GaAsN_alloys_and_As_impurities_in_GaN.

· Poster: Hannu-Pekka Komsa, Jussi Ojanen, Eero Arola, and Tapio Rantala, “First-Principles Electronic Structure Studies on Nitrogen Interstitials in GaAs”. Presented in the Psi-k conference in Schwäbisch Gmünd, Germany, September 17–21, 2005. See this poster here: poster_N_interstitials_in_GaAs.

· Poster: K. Laaksonen, H.-P. Komsa, E. Arola, T. T. Rantala, and R. M. Nieminen, “Electronic and structural properties of GaAsN alloys”. Presented in the XL Annual Conference of the Finnish Physical Society, March 9–11, 2006, Tampere, Finland. See this poster here: poster_GaAsN_alloys_and_As_impurities_in_GaN.

· Poster: Hannu Komsa, Eero Arola, Tapio T. Rantala, Katri Laaksonen, and Risto M. Nieminen, “Computational Study of Defect Formation Energetics in GaAsN”. Presented in the XLI Annual Conference of the Finnish Physical Society, in Tallinn, Estonia, March 15–17, 2007. See this poster here: poster_Defect_Formation_Energetics_in_GaAsN.

First-principles computational studies on electron localization and band offsets at InGaAsN/GaAs and GaAsN/GaAs interfaces

[Carried out as part-time research in the Academy of Finland Project MODEX 2007–2009: “Theory and Modeling of Electronic Excitations in

Nanostructures”]

It is well known by now that optical properties in the GaAsN/GaAs systems and probably also in their related isoelectronic InGaAsN/GaAs systems, are highly sensitive to the atomic and electronic structures at their interfacial region.

Notably, on the basis of our first-principles band offset calculations in the framework of the density functional theory (DFT) and some recent experimental observations, we can conclude that the strain state of the GaAsN layer in the GaAsN/GaAs quantum well (QW) largely influences both its band offset (type of band offset and its value) as well as photoluminescence (PL) properties.

Furthermore, it is obvious that the localized excitonic trap states at the GaAsN/GaAs interface have an effect on not only the PL spectra but also on the band offset itself.

This research has been carried out with Prof. Tapio Rantala (Institute of Physics, Tampere University of Technology) and Prof. Eric Larkins (Photonic and Radio Frequency Engineering Laboratory, University of Nottingham, UK). Prof. Tapio Rantala and Assoc. Prof. Eero Arola acted as supervisors to the PhD student Hannu-Pekka Komsa who carried out the computational activities.

Among our research publications on this topic could be mentioned the following ones:

· Paper: H.-P. Komsa, E. Arola, and T. T. Rantala, “The Band Offset Determination of the GaAs/GaAsN Interface using the Density Functional Theory Method”, J. Phys.: Condens. Matter vol. 20, p. 315004: 1–8 (2008).

· Paper: Hannu-Pekka Komsa, Eero Arola, and Tapio T. Rantala, “Band Offset of InGaAs(N)/GaAs Interfaces from First Principles”, Appl. Phys. Lett. vol. 92, p. 262101: 1–3 (2008).

· Poster: Hannu-Pekka Komsa, Eero Arola, and Tapio T. Rantala, “First-Principles Approach to Band Offsets at GaAsN/GaAs Interface”. Presented in the Conference on Computational Physics 2007 – CCP 2007 in Brussels, Belgium, 5–8 September, 2007. See this poster here: poster_Band_Offsets_at_GaAsN_GaAs_Interface.

· Talk: Hannu-Pekka Komsa, Eero Arola, and Tapio T. Rantala, “Band offset calculation for semiconductor systems with dilute concentration or complex structure”. Presented in the conference on “Theory, Modelling, and Computational methods for Semiconductors (Semiconductor Materials and Nanostructures)” – TMCS 2008, Manchester, UK, January, 2008. See this talk here: talk_Band_Offsets_for_Semiconductor_Systems.

Development, implementation and application of the scissors correction scheme to the complex dielectric function computation for semiconductor systems in the framework of the density functional theory

[Carried out as part-time research in the Academy of Finland Project MODEX 2007–2009: “Theory and Modeling of Electronic Excitations in

Nanostructures”]

It is well known that the density functional theory (DFT) within the framework of the local density approximation (LDA) or the generalized gradient approximation (GGA) largely underestimates the electronic band-gap energy in semiconductors and insulators. Consequently, the real part of the complex dielectric response function will become systematically too large. We have developed and implemented a simple method which allows us to make a correction to the complex dielectric function computed via the DFT within the LDA, GGA, GLLB and GLLB-SC exchange and correlation methods. The correction scheme is based on the use of the scissors operator, i.e. rigidly shifting the conduction bands with respect to the valence bands, in connection with the Kramers-Kronig transformation (KKT).

This research has been carried out with Prof. Tapio Rantala (Institute of Physics, Tampere University of Technology) along with the theoretical PhD students Hannu-Pekka Komsa and Mikael Kuisma (Institute of Physics, TUT) and experimental staff from Optoelectronics Research Centre (ORC), TUT: PhD student Risto Ahorinta (the main experimentalist for our research), Dr Changsi Peng, PhD students Janne Pakarinen and Ville Polojärvi and Prof. Markus Pessa, the Director of ORC. Prof. Tapio Rantala and Assoc. Prof. Eero Arola acted as supervisors to the PhD student Hannu-Pekka Komsa who carried out the computational activities along with Mikael Kuisma.

Among our research publications on this topic could be mentioned the following ones:

· Poster: Eero Arola, Hannu-Pekka Komsa, and Tapio T. Rantala, “A Correction Scheme to the Complex Dielectric Function Computed via the Density Functional Theory”. Presented in the XLI Annual Conference of the Finnish Physical Society, in Tallinn, Estonia, March 15–17, 2007. See this poster here: poster_Scissors_Correction_Scheme_to_Complex_Dielectric_Function.

· Poster: Eero Arola, Hannu-Pekka Komsa, Tapio T. Rantala, Changsi Peng, Risto Ahorinta, Janne Pakarinen, Ville Polojärvi, and Markus Pessa, “Application of Scissors-Correction Scheme to the Calculation of the Complex Dielectric Function for GaAs_1-xN_x Alloys with and without Be-Related Defects”. Presented in the XLII Annual Conference of the Finnish Physical Society, in Turku, Finland, March 27–29, 2008. See this poster here: poster_Scissors_Correction_Scheme_to_CDF_theory_and_application.

· Poster: Eero Arola, Hannu-Pekka Komsa, Mikael Kuisma, and Tapio T. Rantala, “Computational Evaluation of Optical Properties of Band-Gap Materials”. Presented in the Optics Days 2010 of the Finnish Optical Society, in Tampere, Finland, May 6–7, 2010. See this poster here: poster_Scissors_Correction_Scheme_to_CDF_DFT_GLLB_improvement.

First-principles computational studies on electronic, atomic and defect structures in Be-doped GaAs and GaAsN alloys and experimental studies on optical and atomic properties of Be-doped GaInAsN/GaAs quantum wells and GaAs nanocystals

This research has been carried out during the following part-time research posts and post-doctoral contracts:

· Senior Researcher (part-time) in the Academy of Finland Project NEONATE 2006–2008: “New Compound Semiconductor Materials for Optoelectronic Devices” within the Department of Physics, Tampere University of Technology (TUT), Finland.

· Senior Researcher / Project Manager (part-time) of theoretical matters within the Optoelectronics Research Centre, Tampere University of Technology, Finland within the Tekes-funded consortium project NANOPOWER: “Novel polymer nanocomposites for power capacitors”. During 1.6.2011 – 30.4.2014.

The complex and polymorphic dilute nitride semiconductor Ga_1-xIn_xAs_1-yN_y alloys have already for some time been under intensive experimental and to less extent under theoretical studies due to their tunable optical and electronic properties for variety of optoelectronics applications. In contrast to doping effect studies on conventional (Ga,As)Al alloys and the GaN compound the doping effects on dilute nitrides is much less studies and only poorly understood owing to the short- and long-range electronic interactions simultaneously present in polymorphic Ga_1-xIn_xAs_1-yN_y alloys. Interestingly, adding Be dopants into the GaInAsN layer of GaInAsN/GaAs quantum well (QW) structure tremendously improves photoluminescence (PL) properties under thermal annealing and the consequent lasing performance. As our experimental studies clearly shows the improved lasing performance of GaInAsN/GaAs QWs can be attributed to the reduction of out-diffusion of In atoms from the GaInAsN QW layer when it has been doped with Be (p-type doping) [see the paper: Pakarinen et al. (2008) below].

The abovementioned experimental finding has inspired us to carry out first-principles theoretical studies on a large number of neutral and charged Be related defects in GaAs and GaAsN alloy within the framework of the density functional theory (DFT) [see the paper by Komsa et al. (2009) below]. Interestingly, our calculations are among the first such first-principles studies on Be defects in GaAs and GaAsN. Notably, our calculations show that the formation energies of Be derived complex defects such as (Be-N) split interstitials and the substitutional Be – Be interstitial -complex (Be_Ga – Be_I) depend strongly on the place they are located in the GaAsN alloy lattice and on their charge state. Furthermore, our calculations interestingly show that these complex Be derived defects are responsible for the charge-carrier compensation in the Be-doped GaAsN alloy (Be acts as a p-type dopant in GaAs and GaAsN).

Finally, Assoc. Prof. Eero Arola has been involved by carrying out theoretical consultation in two other peer-reviewed publications done related to experimental studies in Optoelectronics Research Centre at TUT. The first of these publications is the paper by Polojärvi et al. (2010) [see below] which considers the improved photoluminescence (PL) optical properties from the GaInAsN/GaAs quantum well (QW) due to (NH₄)₂S and NH₄OH surface treatments during the processing of the QW structure. The second of these publications is the paper by Salminen et al. (2012) [see below] which applies a novel nonlinear optical high-intensity pulsed laser ablation method to fabricate luminescent GaAs nanocrystals. Interestingly, the sizes of the synthesized GaAs nanocrystals (2–10 nm) are essentially smaller than the exciton Bohr radius in the case of bulk GaAs crystal at 300 K (19 nm) leading to optical absorption and emission with tunable wavelengths. In our case the photoluminescence emission was peaked around 530 nm, therefore representing a strong blueshift with respect to bandgap PL emission from the GaAs bulk material.

Among our research publications on this topic could be mentioned the following ones:

· Paper: Hannu-Pekka Komsa, Eero Arola, Janne Pakarinen, Chang Si Peng, and T. T. Rantala, “Beryllium Doping of GaAs and GaAsN from First Principles”, Phys. Rev. B vol. 79, p. 115208: 1–9 (2009).

· Paper: J. Pakarinen, C. S. Peng, V. Poloj¨arvi, A. Tukiainen, V.-M. Korpij¨arvi, J. Puustinen, M. Pessa, P. Laukkanen, J. Likonen, and E. Arola: “Suppression of Annealing-Induced In Diffusion in Be-doped GaInAsN / GaAs Quantum Well”, Appl. Phys. Lett. vol. 93, p. 052102: 1–3 (2008).

· Paper: V. Polojärvi, J. Salmi, A. Schramm, V.-M. Korpijärvi, J. Puustinen, C. S. Peng, A. Tukiainen, M. Guina, M. Pessa, J. Pakarinen, E. Arola, J. Lång, I. J. Väyrynen, and P. Laukkanen: “Effects of (NH₄)₂S and NH₄OH Surface Treatments Prior to SiO₂ Capping and Thermal Annealing on 1.3 μm GaInAsN / GaAs Quantum Well Structures”, Appl. Phys. Lett. vol. 97, p. 111109: 1–3 (2010).

· Paper: Turkka Salminen, Johnny Dahl, Marjukka Tuominen, Pekka Laukkanen, Eero Arola, and Tapio Niemi: “Single-step fabrication of luminescent GaAs nanocrystals by pulsed laser ablation in liquids”, Optical Materials Express vol. 2, pp. 799–813 (2012).

· Paper: E.-M. Pavelescu, N. Baltateanu, S. I. Spanulescu, and E. Arola: “Very high dose electron irradiation effects on photoluminescence from GaInNAs/GaAs quantum wells grown by molecular beam epitaxy”, Optical Materials vol. 64, pp. 361–365 (2017).

First-principles computational studies on the electronic, dielectric and vibrational properties of polymer nanocomposites for power capacitors

This research has been carried out during the following part-time research posts and post-doctoral contracts:

· Senior Researcher (part-time) within the Institute of Electrical Energy Engineering, Tampere University of Technology (TUT), Finland within the Tekes-funded consortium project NANOCAPO: “Nanocomposite Polymer Capacitor Film”. During 1.10.2005 – 31.12.2007.

· Senior Researcher / Person-in-charge (part-time) of theoretical matters within the Department of Physics, Tampere University of Technology, Finland within the Tekes-funded consortium project NANOCOM: “Novel Methods to Formulate Polymer Nanocomposites and Tailor their Dielectric Behaviour”. During 1.1.2008 – 30.4.2011.

· Senior Researcher / Project Manager (part-time) of theoretical matters within the Optoelectronics Research Centre, Tampere University of Technology, Finland within the Tekes-funded consortium project NANOPOWER: “Novel polymer nanocomposites for power capacitors”. During 1.6.2011 – 30.4.2014.

“Electricity and its distribution to customers are in a key role in ensuring human well-being. Insulation materials are a vital part of the components used in a electrical energy distribution network. The shift from ceramic electric insulating materials (e.g. porcelain and glass) and from oil-paper insulations to polymeric materials has been the major change in the field of high voltage insulation technology during the past three decades. Today polymers are widely used in most of the high voltage equipment, e.g. power transformers, insulators, capacitors, reactors, surge arresters, current and voltage sensors, bushings, power cables and terminations. The wide possibilities of the existing polymers and, particularly, the huge scenarios of new polymer compounds in high voltage technology inspires the researchers of the field to innovate and compound new materials and to study their properties and behaviour thoroughly.” (cited from our research funding application for the Tekes consortium project NANOPOWER, see the Scheme of our application, 22 November 2010, p. 3).

The major target of the theoretical part of the Tekes consortium projects NANOCAPO, NANOCOM (see the NANOCOM Project description and the poster_Fortum_Grant_Award_Ceremony_090309_Eero_Arola) and NANOPOWER (see the NANOPOWER Project Agreement) is to create state-of-the-art complex chemical and physical atomic level models of novel polymer nanocomposites and compounds in order to explain and predict their complex dielectric properties such as permittivity and dielectric losses and electrical breakdown strength. Interpretation of macroscopic dielectric behaviour of electrical insulation materials, measured in the laboratories, allows the design of dielectrics with tailored and enhanced properties. For example, our preliminary computational results on isotactic polypropylene (IPP) compounds show, that certain chemical functionalities grafted onto IPP, such as the acrylic acid group (-COOH), can increase the permittivity of hydrocarbon polymers without affecting the electronic band gap. Consequently, there is a chance that in this situation the dielectric strength remains unchanged under acrylic acid grafting. The improved dielectric properties of the modified IPP (IPP grafted with –COOH, NO₂ and SO₃ groups) predicted theoretically, could also be tentatively experimentally verified (see Eero Arola’s 1. talk at the University of Leicester, UK here: talk_First_Principles_Calculations_on_Dielectric_Properties_of_grafted_IPP.

We apply several theoretical approaches in the computational part of the NANOPOWER project:

First of all, the homogeneous polymer compounds, for example, grafted polymers can modeled with the simplest theoretical strategy, namely by molecular polymer chains, oligomers. This is well justified in the situation where the intermolecular interaction between the polymeric chains is sufficiently weak. For example, the van-der-Waals interaction between the polymeric chains should give only a tiny contribution to the polarization phenomena. Polarizabilities of the model molecules are evaluated using the density functional theory (DFT) based calculations from first principles, i.e. without exploiting any experimental information. Consequently, the relation between the macroscopic dielectric constant and the microscopic polarizability of the model molecule is then obtained by using the Clausius-Mossotti relation or its modified modeling (see this Lecture by Assoc. Prof. Eero Arola on the NEIM course during 8–11 December, 2009).

Secondly, in order to tackle the electronic interactions in homogeneous polymer compounds more accurately or those in inhomogeneous polymer systems like polymer nanocomposites, where filler particles are embedded into a polymer matrix, we will use 3-dimensional DFT or density functional perturbation theory (DFPT) based calculations on the dielectric constant. In the cases of acrylic acid (-COOH), NO₂ and SO₃ grafted polypropylene (PP) see my talk in the Nordic Polymer Days in 2010 and my talk in the Nord-IS conference in 2011, and in the case of the calcite nanofiller (CaCO₃ ) – PP system see Assoc. Prof. Eero Arola’s 3. talk at the University of Leicester, UK here: talk_First_Principles_Calculations_on_Dielectric_Properties_of_Nano_Calcite_Filler_IPP.

Thirdly, considering optical properties, we have earlier used first-principles Raman-spectroscopical calculations on polymer molecules (oligomers) using molecular based DFT methods (see Assoc. Prof. Eero Arola’s 2. talk at the University of Leicester, UK here: talk_First_Principles_Raman_Calculations_on_OMPOSS_PP_system). Furthermore, we have recently carried out Raman spectroscopy calculations for a crystalline octamethyl polyhedral oligomeric silsesquioxane (OMPOSS) material using one of the most advanced state-of-the-art solid-state based DFT codes, namely the ABINIT code (see Assoc. Prof. Eero Arola’s 2. talk at the University of Leicester, UK here: talk_First_Principles_Raman_Calculations_on_OMPOSS_PP_system).

Finally, our aim in the NANOPOWER project was to construct and apply a novel “almost unified” theory for dielectric and dielectric breakdown phenomena where ab initio calculations in the framework of DFT are used together with the classical or semi-classical dielectric breakdown modeling (DBM). This challenging task was planned to carry out in collaboration with the University of Leicester research group headed by internationally renowned Prof. John Fothergill after the visit of Assoc. Prof. Eero Arola’s and his PhD student Tommi Kortelainen in Leicester on 18–20 August 2010.

Our Leicester meeting photo can be seen here: photo_Leicester_Meeting_with_the_Research_Group_of_Prof_John_Fothergill_August_2010 (from the left: Prof. Len Dissado, Prof. John Fothergill, Dr Stephen Dodd, Mr Nikola Chalashkanov, Assoc. Prof. Eero Arola and Mr Tommi Kortelainen) and our initial collaboration plan can be seen here: Initial_Collaboration_Plan_between_TUT_and_University_of_Leicester.

This research collaboration initiative can be totally credited to Associate Prof. Kari Kannus from the Department of Electrical Energy Engineering of TUT who organized Prof. John Fothergill to act as an external examiner and opponent in the public defence (24 November, 2010) related to the doctoral dissertation of Markus Takala (“Electrical Insulation Materials towards Nanodielectrics”), the PhD student of Ass. Prof. Kari Kannus. However, due to serious and unexpected financial losses we faced in the NANOCOM project in the end of 2010 and uncertainties whether our follow-up NANOPOWER project application would be funded in 2011 we had to slow down the implementation of this collaboration. Finally, due to the death of my dear colleague and friend, Associate Prof. Kari Kannus in 2013 and the consequent problems in my own research funding at TUT I had to halt this, otherwise so interesting collaboration initiative.

I have carried out the theoretical parts of this research with Prof. Tapio Rantala and Mr Tommi Kortelainen (Institute of Physics, TUT) along with Prof. Seppo Valkealahti and his postdoctoral researcher Henna Ruuska (Institute of Electrical Energy Engineering, TUT). Concerning the experimental parts of polypropylene (PP) nanocomposites research I have worked with Associate Professor Kari Kannus (Institute of Electrical Energy Engineering, TUT), Prof. Mika Pettersson and Mrs Suvi Virtanen (Department of Chemistry, University of Jyväskylä) and Mikko Karttunen (VTT, Technical Research Centre of Finland). Finally, concerning the Structural and Dielectric Properties of (La, Nd) (Mg1/2Ti1/2)O3 Perovskites for microwave resonator applications I have worked with Lic.Tech. Kouros Khamoushi (Institute of Electrical Energy Engineering, TUT).

Among our research publications on this topic could be mentioned the following ones:

· Paper: Henna Ruuska, Eero Arola, Kari Kannus, Tapio T. Rantala, and Seppo Valkealahti: “Feasibility of Density Functional Methods to Predict Dielectric Properties of Polymers”, J. Chem. Phys. vol. 128, p. 064109: 1–12 (2008).

· Paper: Henna Ruuska, Eero Arola, Tommi Kortelainen, Tapio T. Rantala, Kari Kannus, and Seppo Valkealahti: “A Density Functional Study on Dielectric Properties of Acrylic Acid Grafted Polypropylene”, J. Chem. Phys. vol. 134, p. 134904: 1–14 (2011).

· Paper (conference): Eero Arola and Tommi Kortelainen: “Electronic and Dielectric Properties of Acrylic Acid Grafted Polypropylene from First-Principles Calculations”, in Nordic Insulation Symposium 2011 (Nord-IS 11), June 13–15, Tampere, Finland. The paper can be seen here: paper_First_Principles_Calculations_on_Acrylic_Acid_Grafted_Polypropylene.

· Paper (conference): Kouros Khamoushi and Eero Arola: “Structural and Dielectric Properties of (La, Nd) (Mg_1/2Ti_1/2 )O₃ Perovskites”, in Nordic Insulation Symposium 2011 (Nord-IS 11), June 13–15, Tampere, Finland. The paper can be seen here: paper_Structural_and_Dielectric_Properties_of_La_Nd_Mg_1_2Ti_1_2O_3_Perovskites.

· Paper (conference): Suvi Virtanen, Tommi Kortelainen, Susanna Ahonen, Viivi Koivu, Manu Lahtinen, Eero Arola, Mikko Karttunen, Satu Kortet, Kari Kannus, and Mika Pettersson: “Characterization of Octamethylsilsesquioxane (CH₃)₈Si₈O₁₂ Fillers in Polypropylene Matrix”, in Nordic Insulation Symposium 2011 (Nord-IS 11), June 13–15, Tampere, Finland. The paper can be seen here: paper_Characterization_of_Octamethylsilsesquioxane_Fillers_in_Polypropylene_Matrix.

· Invited talk: E. Arola: “Modeling and calculation of dielectric properties of polymeric insulation materials”. This 3-hour lecture was presented in the international PhD course Novel Electric Insulation Materials (NEIM), in the Department of Electrical Energy Engineering, Tampere University of Technology, Finland, December 8–11, 2009. The talk can be seen here: invited_talk_Modeling_Dielectric_Properties_of_Polymeric_Insulation_Materials.

· Invited talk: E. Arola, T. Kortelainen, T. T. Rantala, H. Ruuska, K. Kannus, and S. Valkealahti: “Computational solid state physics of polymers”. Presented in the 6th Workshop of the Tekes consortium project NANOCOM (Novel Methods to Formulate Polymer Nanocomposites and Tailor their Dielectric Behaviour) meeting, Tampere University of Technology, Finland, December 3, 2009. The program for this workshop was organized by Docent Eero Arola and MSc Tommi Kortelainen. The talk can be seen here: invited_talk_Computational_Solid_State_Physics_of_Polymers.

· Talk: Henna Ruuska, Eero Arola, Kari Kannus, Seppo Valkealahti, and Tapio T. Rantala: “Computational Studies on Electronic and Dielectric Properties of Polymer Compounds”. Presented in the XL Annual Conference of the Finnish Physical Society, March 9–11, 2006, Tampere, Finland. The talk can be seen here: talk_First_Principles_Computational_Studies_on_Polymer_Compounds.

· Talk: Eero Arola, Henna Ruuska, Tommi Kortelainen, Tapio T. Rantala, Kari Kannus, and Seppo Valkealahti: “Dielectric Properties of Acrylic Acid Grafted Polypropylene from First-Principles Calculations”. Presented in the Nordic Polymer Days 2010 conference, organized by the Society for Wood and Polymer Chemistry in Finland, in Helsinki, Finland, May 24–26, 2010. The talk can be seen here: talk_First_Principles_Dielectric_Calculations_on_Acrylic_Acid_Grafted_PP.

· Talk: Eero Arola and Tommi Kortelainen: “Electronic and Dielectric Properties of Acrylic Acid Grafted Polypropylene from First-Principles Calculations”. Presented in the Nordic Insulation Symposium 2011 (Nord-IS 11), June 13–15, Tampere, Finland. The talk can be seen here: talk_First_Principles_Electronic_and_Dielectric_Calculations_on_Acrylic_Acid_Grafted_PP.

· Poster: H. Ruuska, E. Arola, K. Kannus, S. Valkealahti, and T. T. Rantala: “Density Functional Studies on Polarizability and Permittivity of Polymers”. Presented in the XLI Annual Conference of the Finnish Physical Society, in Tallinn, Estonia, March 15–17, 2007. See this poster here: poster_DFT_Studies_on_Polarizability_and_Permittivity_of_Polymers.

· Poster: E. Arola: “Density functional studies on high-voltage dielectric properties of polymer nanocomposites”. Presented in the research grants award ceremony, organized by the Fortum Foundation in Keilaniemi, Espoo, Finland, March 9, 2009. See this poster here: poster_DFT_Studies_on_High_Voltage_Dielectric_Properties_of_Polymer_Nanocomposites.

· Poster: Tommi Kortelainen, Eero Arola, Susanna Ahonen, Suvi Virtanen, Jani Pelto, Kari Kannus, and Mika Pettersson: “Raman Spectroscopical Studies of Crystalline Octamethylsilsesquioxane (CH3)8Si8O12 in Polypropylene Matrix”. Presented in the Nordic Polymer Days 2010 conference, organized by the Society for Wood and Polymer Chemistry in Finland, in Helsinki, Finland, May 24–26, 2010. See this poster here: poster_Raman_Studies_of_Crystalline_Octamethylsilsesquioxane_PP_Matrix.

· Poster: Kouros Khamoushi and Eero Arola: “Structural and Dielectric Properties of (La, Nd) (Mg1/2Ti1/2)O3 Perovskites”. Presented in Nordic Insulation Symposium 2011 (Nord-IS 11), June 13–15, Tampere, Finland. See this poster here: poster_Structural_and_Dielectric_Properties_of_La_NdMg1_2Ti1_2O_3_Perovskites.

Modeling High-Intensity Ultra-Short Laser-Pulse Induced Multiphoton Absorption and Dielectric Breakdown (Ablation) in Dielectric Insulator Materials (scientific research consultation)

[Carried out as part-time consulting research for the Corelase company during 2011 – 2014]

Assoc. Prof. Eero Arola has carried out scientific theoretical research consulting for the international Corelase company (headquarters in Rusko, Hervanta, Finland) during 2011 – 2014. The Corelase company manufactures high-intensity pulse lasers and sells them worldwide. The consulting work has included theoretical development and implementation of the multiphoton absorption phenomena for high-intensity ultra-short laser pulses in sapphire. This development project has been done in close collaboration with Dr Harry Asonen, the CEO of Corelase. As a result of his consultation project Dr Arola has developed and implemented a semi-empirical quantum mechanical code which can estimate the required laser beam intensities which are able to produce dielectric breakdown, i.e. ablation phenomenon in the sapphire crystal. Dr Arola has published this work in the publications:

· Research Report to Corelase (confidential): Eero Arola, “Multi-Photon Absorption in Ultra-Short Laser Pulse Processing of Sapphire Wafers”, 19 pages, published in 21 December, 2011.

· Paper: E. Arola, “Theoretical Studies on Multiphoton Absorption of Ultra-Short Laser Pulses in Sapphire”, Journal of Quantum Electronics vol. 50, pp. 709–720 (2014).

Research Experience in Great Britain

First-principles relativistic magnetic x-ray resonant scattering (MXRS) theories for ordered and disordered magnetic materials in the framework of the relativistic density functional theory (RDFT)

This research has been carried out during the following full-time Post-Doctoral Research Fellow Posts:

· Visiting Research Fellow at University of Bristol, UK, funded by the Academy of Finland and the Royal Society. Duration 1.11.1992 – 30.6.1994.

· Post-Doctoral Research Fellow post (invited) at Keele University, UK, funded by the EPSRC (UK). Duration 20.2.1995 – 19.8.1997.

· Post-Doctoral Research Fellow post (invited) at Keele University, UK, funded by the EPSRC (UK). Duration 1.4.1999 – 31.3.2001.

In contrast to the fixed-wavelength x-ray radiation sources commonly used, for example, in x-ray diffractometers, the presently available fourth-generation high-intensity, high-resolution and wavelength tunable synchrotron radiation sources have opened new possibilities to tackle a wide range of new physical phenomena and properties of materials, previously not accessible to conventional x-ray diffractometers.

Notably, when the photon energy is tuned through an absorption edge of a constituent, a large and species selective enhancement of the scattering cross section occurs (resonant, anomalous scattering). Consequently, in the case of magnetic materials it is noticeable that by using the resonant scattering it is possible to overcome the weak magnetic x-ray scattering which is smaller than that for charge scattering by the order of . Remarkably, using polarization properties of x rays it is possible to distinguish between orbital and spin scattering, unlike in the neutron case.

However, in order to exploit the novel synchrotron radiation facilities in magnetic materials research accurately and reliably requires almost invariably theoretical modeling in connection with the experiments. For this reason, I developed and implemented two major state-of-the-art and unique first-principles formalisms and their specific theoretical applications for magnetic scattering of circularly polarized x rays from magnetic solids within the fully relativistic spin-polarized density functional theory (R-SP-DFT) during these post-doctoral research contracts:

· The Academy of Finland and the Royal Society Research Fellow at University of Bristol, UK, during November 1992 – June 1994 with Prof. Balazs L. Gyorffy and Dr Paul Strange.

· I was invited to the EPSRC post-doctoral research fellow post at Keele University, UK to work with with Prof. Paul Strange during February 1995 – August 1997.

· I was invited to the EPSRC post-doctoral research fellow post at Keele University, UK to work with Prof. Paul Strange during April 1999 – March 2001.

The two theoretical formalisms for MXRS and their specific theoretical applications are the following ones:

1. The first such formalism has been implemented in the framework of the fully relativistic spin-polarized multiple-scattering theory (E. Arola, P. Strange and B. L. Gyorffy, “Relativistic theory of magnetic scattering of x rays: Application to ferromagnetic iron”, Physical Review B vol. 55, p. 472, 1997).

i. Theory application 1: This formalism (E. Arola et al., PRB 1997) has also been extended from magnetic metals to magnetic substitutional binary alloys within the Kohn-Korringa-Rostoker Coherent Potential Approximation (KKR-CPA). For details, see E. Arola, P. Strange, N. I. Kulikov, M. J. Woods and B. L. Gyorffy, “Application of the relativistic theory of magnetic scattering of X-rays to ferromagnetic Fe and Cr₄₇Fe₅₃ alloy”, Journal of Magnetism and Magnetic Materials vols. 177–181, p. 1415, 1998. A more detailed description of this application theory can be found in our poster_MXRS_alloy we presented in Cairns, Australia in August 1997.

ii. Theory application 2: We have adopted our formalism (E. Arola et al., PRB 1997) with slight modifications in order to calculate the diffraction anomalous fine structure spectra (DAFS) in Cu. We demonstrate the ability of our formalism to interpret the crystalline environment related near-edge fine structure features in the resonant x-ray scattering spectra at the Cu K absorption edge. We find good agreement between the computed and measured diffraction anomalous fine structure features of the x-ray scattering spectra. For details, see E. Arola and P. Strange, “Application of relativistic scattering theory of x rays to diffraction anomalous fine structure in Cu”, Physical Review B vol. 58, p. 7663, 1998”.

2. The second formalism has been implemented in the framework of the relativistic spin-polarized linear muffin-tin orbital with atomic sphere approximation band structure calculation method including the self-interaction corrections (SIC) [E. Arola, M. Horne, P. Strange, H. Winter, Z. Szotek and W. M. Temmerman, “Self-Interaction corrected relativistic theory of magnetic scattering of x rays: Application to praseodymium”, Physical Review B vol. 70, p. 235127, 2004].

We have also presented our theoretical MXRS and MX Absorption studies in several other publications, talks and posters:

· Paper 1: P. Strange, E. Arola, and B. L. Gyorffy, “Theory of Magnetic X-Ray Absorption Dichroism”, Journal of Magnetism and Magnetic Materials vols. 140–144, pp. 73–74 (1995).

· Paper 2: E. Arola and P. Strange, “Relativistic Theory of Magnetic X-Ray Scattering”, Applied Physics A vol. 73, pp. 667–671 (2001).

· Poster: E. Arola, P. Strange, and B. L. Gyorffy, “Relativistic Theory of Magnetic Scattering of X-Rays from Transition Metals”. A presentation (poster) in the European Research Conference on Electronic Structure of Solids: Itinerant Magnetism, Lunteren, The Netherlands, 9–14 September, 1995.

· Poster: E. Arola, P. Strange, N. Kulikov, C. F. Hague, and B. L. Gyorffy, “Applications of the Relativistic Theory of Magnetic Scattering of X-Rays to Ferromagnetic Fe and Fe-Cr alloys”. Presented in the International Conference on Magnetism 1997 incorporating The Symposium on Strongly Correlated Electron Systems 1997, Cairns Convention Centre, Australia, July 27–August 1, 1997. Hosted by the Australian Institute of Physics. See this poster here: poster_MXRS_alloy.

· Poster: E. Arola, P. Strange, N. I. Kulikov, M. J. Woods, and B. L. Gyorffy, “Application of the Relativistic Theory of Magnetic Scattering of X Rays to Ferromagnetic Fe and Cr47Fe53 alloy”. Presented in the Condensed Matter and Materials Physics Conference 1997 (CMMP 97) at the University of Exeter, UK, December 17–19, 1997. Organised by the Institute of Physics (IOP).

· Poster: E. Arola, P. Strange, N. Kulikov, M. J. Woods, and B. L. Gyorffy: “Application of the Relativistic Theory of Magnetic Scattering of X-Rays to Ferromagnetic Fe and Cr47Fe53 alloy”. Presented in the International Workshop on Nonlinear Magneto-Optics at the Leeuwenhorst Congress Centre, Noordwijkerhout, The Netherlands, June 26–28, 1998. Supported by TMR-network NOMOKE.

· Poster: E. Arola, P. Strange, N. Kulikov, M. J. Woods, and B. L. Gyorffy, “Application of the Relativistic Theory of Magnetic Scattering of X-Rays to Ferromagnetic Fe and Cr47Fe53 alloy”. Presented in the International Workshop on NONLINEAR MAGNETO-OPTICS in Cardiff, UK, June 24–26, 1999. Supported by TMR-network NOMOKE.

· Poster: E. Arola, M. Horne, P. Strange, W. M. Temmerman, Z. Szotek, and H. Winter, “Theory of Magnetic X-Ray Scattering From Rare Earth Materials”. Presented in the Condensed Matter and Materials Physics Conference – CMMP 2002, Brighton, April 7–11, 2002.

· Invited Talk: E. Arola: “Relativistic theory of magnetic scattering of x rays from first-principles: Applications to metals and alloys”. Presented in the Symposium on Atomic-Scale Challenges in Advanced Materials (ASCAM III), the Department of Physics, University of Turku, Finland, August 20–21, 2007. See the talk here: Invited_talk_Relativistic_MXRS_theory_and_applications.

It is quite remarkable that our relativistic magnetic x-ray scattering theories we have implemented are capable of reproducing experimental results from magnetic metals and alloys in good or even excellent agreement. A particularly good example of such an excellent agreement between our experiments and theoretical calculations based on the paper by E. Arola et al., Phys. Rev. B vol. 70, p. 235127 (2004) can be found in the following paper: S. D. Brown, P. Strange, L. Bouchenoire, B. Zarychta, P. B. J. Thompson, D. Mannix, S. J. Stockton, M. Horne, E. Arola, H. Ebert, Z. Szotek, W. M. Temmerman, and D. Fort, “Dipolar Excitations at the L_III X-Ray Absorption Edges of the Heavy Rare-Earth Metals”, Physical Review Letters vol. 99, p. 247401 (2007). This paper demonstrates how our theoretical calculations can reproduce with excellent agreement the measured dipolar (E1) asymmetry ratio spectra at the L_III absorption edges of the heavy f-electron rare-earth metals (Gd, Tb, Dy, Ho, Er and Tm).

Towards relativistic linear and nonlinear laser-spectroscopic theories for magnetic materials from first principles within the time-dependent density functional theory (TDDFT)

This research has been carried out during the following full-time Post-Doctoral Research Post (invited post, funded by the EPSRC, UK):

· Post-Doctoral Research Officer post at the University of Bath, UK. Duration 1.9.1997 – 28.2.1999.

Clearly, our research objectives behind the abovementioned title has been a very, very ambitious task which obviously no one in the world has yet been able to work out at the time I started to work as an invited EPSRC post-doctoral research fellow for this theoretical research project at the University of Bath during September 1997 – February 1999 with Dr Simon Crampin. No wonder, even up to date such theory being able to incorporate accurately the complex linear and nonlinear light-matter interactions in realistic magnetic solids with interfaces has obviously not been developed and implemented. However, during this relatively short period of my post-doctoral research post we were able to develop some approximate theories related to linear and nonlinear light-matter interactions in solids and solid surfaces in the collaboration with Prof. John Inglesfield and Dr Lionel Calmels from the University of Wales, in Cardiff. These studies have been presented in several publications, talks and posters:

1. Paper 1: L. Calmels, J. E. Inglesfield, E. Arola, S. Crampin, and Th. Rasing, “Local-Field Effects on the Near-Surface and Near-Interface Screened Electric Field in Noble Metals”, Physical Review B vol. 64, p. 125416: 1–8 (2001).

2. Paper 2: L. Calmels, J. E. Inglesfield, S. Crampin, E. Arola, and Th. Rasing, “Complex Frequency Technique for Linear and Second Harmonic Optical Properties of Metallic Surfaces”, Computer Physics Communications vol. 151, pp. 251–264 (2003).

3. Invited Talk: E. Arola, S. Crampin, J. E. Inglesfield, and L. Calmels, “Relativistic Scattering Theory of Magnetic Second Harmonic Generation from Magnetic Metals”. Presented in the KKR [Korringa - Kohn - Rostoker method] meeting, Daresbury Laboratory, Warrington, UK, February 17, 1999.

4. Talk: E. Arola, S. Crampin, J. E. Inglesfield, and L. Calmels, “Aspects about the Relativistic Spin-Polarized LKKR-MSHG Theory”. Presented in the international conference on the Interface Magnetism in Modane, France, March 27–April 1, 1999. Organized by the European Psi-k Network.

5. Talk: E. Arola, S. Crampin, L. Calmels, and J. E. Inglesfield, “Aspects about the Relativistic Spin-Polarized LKKR-MSHG Theory”. Presented in the International Workshop on Nonlinear Magneto-Optics at the Leeuwenhorst Congress Centre, Noordwijkerhout, The Netherlands, June 26–28, 1998. Supported by TMR-network NOMOKE.

6. Talk: E. Arola, S. Crampin, L. Calmels, and J. E. Inglesfield, Talk about the Layer-KKR (LKKR) electron structure method for surfaces and interfaces. Presented in the TMR nonlinear magneto-optical Kerr-effect (NOMOKE) meeting at the Orsay University, November 21, 1997. The meeting was arranged by Pierre Beauvillain, Director de Recherches CNRS, Institut d’Electronique Fondamentale Bat 220, Universite Paris-Sud, 91405 Orsay, France.

7. Poster: E. Arola, S. Crampin, L. Calmels, and J. E. Inglesfield, “Relativistic Scattering Theory of Magnetisation Induced Second Harmonic Generation (MSHG)”. Presented in the International Workshop on NONLINEAR MAGNETO-OPTICS in Cardiff, UK, June 24–26, 1999. Supported by TMR-network NOMOKE. You can have a look at this poster here: poster_MSHG_theory.

---

ã Eero Arola March 24 2024