EUSpec Modern Tools for Spectroscopy on Advanced Materials

Jan Minar

NTC, Plzen, Czech

Ti doped ZnO thin films

During the STSM stay, I learned how to use the code (SPR-KKR package): Create the system, enter the input files, run the calculation and interpret the results. I carried out the calculations I needed to do on Ti doped ZnO: EELS for Ti-l edge and O-K edge, Ti 2p core level and XAS for ZnO when Ti is in a substitutional position and interstitial position and for ZnTiO3 as well.

Alberto Marmodoro

Dept. Chemie, LMU Munich, DE

Didier Sebilleau

Univ de Rennes, FR

Implementation of an interface between SPR-KKR and MsSpec

Purpose of this STSM was to continue and bring to fruition interoperability work between the Munich “Spin-Polarized Relativistic Korringa, Kohn, Rostoker” (SPRKKR) package by Prof. Hubert Ebert (Ludwig Maximilians Universität,Munich, Germany), and the family of single-site / multiple-scattering spectroscopy codes developed by the STSM host, Dr. Didier Sébilleau, at the Institute of Physics, Universitè de Rennes 1; and Prof. Calogero Natoli (Laboratori Nazionali di Frascati (LNF) / Istituto Nazionale di Fisica Nucleare (INFN), Italy). The different groups share a common theoretical framework for the mathematical description of spectroscopy experiments within a multiple scattering formalism. This goal has been pursued with the production of initially independent software packages, that have specialized on particular aspects of the general task. After realizing the possibility of ruitful synergy across the partially overlapping respective areas of interest, various collaboration channels have been set up over recent years. This STSM represents continuation of such activities along a specific prospective, namely the implementation of a software compatibility interface between the SPRKKR package and the host code(s). 

Jakub Schusser,

Université de Cergy Pontoise, Neuville, FR

Jan Minar

NTC, University of West Bohemia, Pilsen, CZ

Introduction to the SPR-KKR program package

The aim of this STSM grant was to be able to compare the results obtained from the experiment with the theoretical calculations - thin films (one or several monolayers) of MoSe2, MoS2 and MoTe2 using photoelectron spectroscopy (XPS, UPS, ARPES). The STSM grand holder has learned to use the SPR-KKR code in order to be able to make simulations of basic and more structurally advanced bulk models of crystals and the basic surface structures. The grant holder is now able to define the structure type, space group, surface of the 3D system with different Miller indices and to understand the basic parameters used in calculations, to create the input file for the calculation and to calculate the potential of the system which will later be used to calculate Bloch spectral function, density of states and ARPES spectra. Due to the understanding the basics of the code, the grant holder is also able to provide with the basic interpretation of the calculation result and comparing it with the experimental results. This STSM was strongly related to WG2: Spectroscopy as well as WG5: Experiment.

Andrea Marini,

Istituto di Struttura della Materia-CNR, Rome, IT

Time-dependent optical properties of 2D transition metal dichalcogenides

The main aim of the STSM was the theoretical study of the optical properties of two-dimensional transition metal dichalcogenides (TMDs) by means of first principles calculations. The purpose of my visit was to obtain hands on experience in running simulations using the Yambo code and perform calculations of the excited state properties of TMDs. After a full DFT calculation using Quantum Epsresso for both bulk and 2D hBN, the databases for the Yambo run were initialized and different approximations (HF, GW, PPA) were tested. The experience gained during the STSM was then used for calculations on 2D TMDs as well as on the various polytypes of SiC. A realistic Yambo calculation of the time-dependent optical properties of these materials under intense laser pulses will be compared with recent experimental results. Therefore the present STSM contributes to WG2: Spectroscopy and WG3: Time-resolution. The obtained results may also trigger experimental efforts and thus contribute to WG5: Experiment

Sylvain Tricot

Univ de Rennes, FR

Hubert Ebert

Department Chemie, Physikalische Chemie, LMU Munich, DE

An inroduction to the SPR-KKR package for computing magnetic properties

The purpose of this STSM was to use SPRKKR to compute magnetocrystalline anisotropies (MCA) to model experimentally observed results on Fe/Au/Fe spin valve onto Silicon. Hot electron magnetoconductance effects are expected in these fully epitaxied devices. Magnetic measurements on this structure revealed that iron electrodes do not exhibit any MCA. We suspect the presence of silicon into the iron layers to be responsible for these unexpected properties. During this STSM, we started an investigation of these hypotheses by computing the magnetic properties of this system. These results should be coupled to X-Ray photodiffraction experiments and to a multiple scattering simulation of this spectroscopy by the MsSpec code. Thus, this STSM would contribute to WG2: Spectroscopy.

Lars Nordsträm

Uppsala University, Uppsala, SE

Interfacing ELK and Wannier90: a basis for DFT+DMFT calculations

The goal of this STSM was to develop an interface for the computational code based on the density functional theory (DFT), called ELK, and computational tool Wannier90, which is used to construct Wannier functions. The developed interface allows combining the advantages of these two computing codes: DFT is realized in ELK using an all-electron full-potential linearized augmented-plane-wave method (FP-LAPW), which is versatile and applicable for a wide range of bulk materials, even those containing heavy elements, complex polyatomic systems, as well as to open structures - surfaces, clusters, organic and inorganic molecules; electronic structure information provided by ELK is used to generate in Wannier90 the maximally-localized Wannier functions (MLWF), that provide a compact tight-binding parameterization of the original material’s band structure and is used to address strong correlation effects and non-collinear topological magnetism. Developed interface will be incorporated in the latest version of Elk code [http://elk.sourceforge.net]. The STSM contributes to WG1 Correlation, WG2 Spectroscopy and WG4 Platform.

Martin Lueders,

UKIR STFC, Daresbury, UK

Development and collaboration on the ESCDF library

The purpose of the STSM was to accelerate the design and development of the Electronic Structure Common Data Format (ESCDF) specifications and the associated libraries. During the STSM an agreement has been reached on the specifications for the basis sets, several design flaws have been corrected, and the library now includes working implementation of the latest specifications of the systems group.

Computational approach to the optical absorption spectra of molecules

The purpose of the STSM was to study, within a theoretical/computational GW / BSE scheme, the optical properties of some dibenzochrysene derivatives, for their potential role in optoelectronic applications. During the staying we have used the FIESTA package to perform simulations that aims to investigate the optical absorption spectra of molecules based on the two different aromatic dibenzochrysene cores (angular and compact) with a large kind of functional groups. After the calculations we have compared the obtained results with experimental data and we have found a general fair agreement of our results with the experimental data available in the literature.

Study of the interaction of catechin molecules with lipids

The purpose of the STSM was to discuss about the interactions of catechins with lipids. The main goal of this collaboration is to determine the physical processes and the molecular mechanisms underlying the action mode of catechins in order to understand how these compounds interact with lipids and other biological molecules using both experimental and theoretical methods. The STSM initiated a fruitful collaboration between the two involved institutions that is continued in the future. 

The study of dichroic effects in strongly correlated systems

The STSM purpose was to implement spherical tensor analysis of X-ray absorption and Resonant inelastic X-ray spectroscopy in the quantum many body script language Quanty. We further applied our methodology to simulate linear and circular magnetic dichroic effects in the archetype magnetic oxide: magnetite.

Didier Sebilleau

Univ de Rennes, FR

Hubert Ebert

Department Chemie, Physikalische Chemie, LMU Munich, DE

Ab initio potential for MsSpec

The purpose of this STSM was to write an interface program between the Munich code SPR-KKR and the Rennes code MsSpec. With this interface program, it is now possible to import in the spectroscopic MsSpec code the ab initio potential and charge density calculated by SPR-KKR. 

Diana Harea

Inst. Of appl. Physics of Academy of Sciences of Moldovia Chisinau, MD

Simon Rittmeyer

Dept. Chemie TUM Munich, DE

Jörg Meyer

Univ. Leiden, NL

Non-Adiabatic Electron-Hole Pair Excitation Spectra for Surface Dynamics

The STSM was dealing with the validation of a perturbative approach to evaluate non-adiabatic electron-hole pair excitation spectra for surface dynamical phenomena and concomitant energy losses. Moreover, the outcomes have been compared to those obtained via the electronic friction approach that has become very popular recently. Intriguing deviations from the latter with respect to experimentally measured vibrational lifetimes have been found. Finally, an experimental spectroscopic measure was proposed to verify these findings. Thus, the STSM contributes to WG2: Spectroscopy, WG4: Platform and should inspire efforts within WG5: Experiment.

Diana Ancuta Benea

Babesbolyai Univ. Cluj-Napoca, RO

Jan Minar

Dept. Chemie, LMU Munich, DE

Correlation effects in positron annihilation 2D-ACAR spectra

The purpose of the STSM was to reveal the possible influence of correlation effects in the 2D-ACAR (two-dimensional angular correlation of positron annihilation radiation) spectra for some specific materials (3d metals and half-metallic systems). A corresponding study was performed by including the effects of strong electron-positron attraction and the electron-electron correlations within the SPR-KKR calculations. Thus the STSM mainly contributed to WG1 correlation and to WG2 spectroscopy. The results of this study will be reported on occasion of the 2017 Working Group meeting in Prague.

Károly Tőkési

Inst. Of Nuclear Research ATOMKI Debrecen, HU

Dusko Borka

Vinca Institute of Nuclear Sciences, Belgrade, RS

Simulation of backscattered electron spectra at grazing scattering geometry

The issue investigated of the STSM was the simulation of the backscattering electron spectra from solid surfaces. The attention was focused on the investigation of the grazing scattering geometry. The classical transport code of the collaborating partners could be substantially improved including five independent layers as a sandwich in the simulations. In case that one considers one single material the first layer can mimic the surface while the second layer can mimic the bulk. This work contributes to WG2: Spectroscopy as well as and WG5 Experiment.

Dr Basile Curchod

Univ. of Bristol UK

Federica Agostini

MPI for Microstructurphysics Weinberg, DE

Conical intersection – a mirage within the exact factorization of the molecular wavefunction

During the STSM stay the dynamics of a nuclear wave packet through a conical intersection as depicted in the exact factorization formalism was studied. The exact factorization indeed offers a new paradigm for the description of nonadiabatic events - based on time-dependent potentials - and does not depend on an electronic representation. Based on a two-dimensional model system, it was observed that the familiar topological features of Born-Oppenheimer potential energy surfaces around a conical intersection do not appear in the time-dependent potentials of the exact factorization, which remain smooth even in the intersection region. This knowledge is crucial to the development of approximate methods for excited-state dynamics, which will eventually be beneficial for the interpretation and the prediction of spectroscopic outcomes. Hence, this visit led to fundamental results relevant to the WG3 Time-resolution, but also to the WG1 Correlation for the more fundamental part.

George Tsibidis

Inst. of Electronic Structure + Laser Heraklion, EL, GR

Olivier Uteza

Lab. LP3, Marseille, FR

Modelling of damage thresholds on dielectrics after irradiation with ultrashort laser pulses

The aim of the STSM was to perform a combined theoretical and experimental investigation of the fundamental mechanisms after irradiation of dielectrics (i.e. fused silica) with ultrashort pulsed lasers. The work aims to lead to the development/revision of a theoretical model and a corresponding computational code that will describe electron excitation in dielectrics and relaxation processes and eventually to associated morphological changes; i.e. therefore an estimation of damage thresholds, melting threshold, etc. For these transient changes of electron/lattice temperature, vibrational modes, plastic effects have been analysed. Accordingly, the activity of the STSM is closely related to the WGs 4 and 5.

Ieva Kranauskaite

Vilnus Univ. LT

Maria Raposo

Faculty of Schience and Technology, Nova Univ. of Lisbon, PT

Organic thin film preparation and characterization

The aim of the STSM was to prepare organic thin films using a layer-by-layer technique and characterize them for further investigations at the home institution. The samples have been successfully prepared and investigated by broadband impedance spectroscopy, with the results further to be analysed. The STSM initiated a fruitful collaboration between the two involved institutions that is continued in the future.

Dusan Nikezic

Vinca Institute of Nuclear Sciences, Belgrade, RS

Didier Sebilleau

Univ de Rennes, FR

Parallelization of MsSpec with NVIDIA Fortran

During the STSM stay program developments on MsSpec were made in close collaboration with Dr. Keisuke Hatada to speed up the code using MAGMA software for a hybrid architecture CPU/GPU. The MAGMA project aims to develop a dense linear algebra library similar to LAPACK but for heterogeneous/hybrid architectures, starting with current ""Multicore+GPU"" systems. The corresponding example code of MAGMA which is a version for LAPACK for GPU was modified according to the needs of MsSpec. The necessary PGI CUDA Fortran license was bought by Dr. Keisuke Hatada. This project work contributes to WG5 platform and provides valuable information and developments for this powerful computer architecture.

Diana Harea

Inst. Of appl. Physics of Academy of Sciences of Moldovia Chisinau, MD

Radek Stocek

Center of Polymer Systems, Univ. Tomas Bata, Zlin, CZ

Calculation of general infrared parameter identifying binary and ternary rubber blends from the obtained infrared IR spectra

The project contributed to the subjects and goals of the Action by introducing a new theoretical scheme to deal with experimental data. The idea is to obtain the exact peak heights from the original experimental IR spectra by subtraction of an appropriate baseline. This baseline is constructed using a numerical algorithmic method that was developed recently by Radek Stocek’s group. Corresponding applications aimed to get more experience on the computational algorithm and at a deeper understanding of the interaction between ternary blends and radiation. This way the STSM contributes to the establishing of new theoretical schemes within WG2 spectroscopy.

Xavier Roquefelte

ISCR UMR CNRS 6226 Rennes, FR

Peter Blaha

TU Vienna Inst. Of Materials Chemistry Vienna, AT

Ab-initio calculations together with XANES measurements

During his stay in the group of Prof. Peter Blaha (TU WIEN), the grantee and host have worked together in a combined experimental and theoretical project on Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy of C60 and (C59N)2. With the results published recently in a highly ranked journal. During the stay, the common work has been extended to the simulation of NEXAFS spectra of C60 and C70 using the WIEN2k code that was made available in the past within the EUSpec training school in Slovenia. The project contributed to WG2 Spectroscopy by stringly linking experiment and theory and exploring new fields of spectroscopy for established computer codes.

Marius Retegan

ESRF Grenoble, FR

Maurits Haverkort

MPI for Chemical Physics of Solids Dresden, DE

A graphical user interface for core-level spectroscopy simulations

The main goal of the mission was to extend Crispy a core-level spectroscopy oriented graphical user interface developed at the ESRF to include more of the capabilities present in the Quanty software that was made available in the past within a EUSpec training school in Pilsen. This way new users will get an easy access to the rather new program package that offers an important scheme to deal with multiplets in core level spectroscopy. The STSM contributes to WG1 correlation and WG2 spectroscopy. The result was highlighted in the 4th EUSpec newsletter.

Emille Bruyer

Inst. De Sciences Chimiques Rennes, FR

Silvia Picozzi

Consiglio Nazionale delle Ricerche Chieti, IT

Ab-initio calculations together with ARPES measurements

Discussions and calculations were made on various issues with the aim to supply via first-principles calculations a full explanation of the magnetic and electronic structure of materials showing strong spin-orbit-driven properties. This way a direct comparison of theoretical results with experimental ARPES spectra of IrO2 and corresponding discussions could be made. In addition a study that combined DFT calculations and the tight-binding model revealed the structure-dependence of Rashba-like spin splitting observed in GeTe. This common work contributes to WG1 correlation and WG2 spectroscopy by strengthening the interaction between experiment and theory and initiating the development of new theoretical tools.

Ondrej Sipr

Fyzikalni ustav Akademie ved Ceske republiky Praha, CZ

Hubert Ebert

LMU Munich, DE

Influence of the spin-orbit coupling on the magnetic dipole term

The purpose of the STMS was to discuss and analyse numerical results concerning the so called Tz term for Co monolayers and Co adatoms of 3d elements on the (111) surfaces of Cu, Ag, Au, Pd, and Pt contributing this way to WG2 spectroscopy. In addition, the topic directly concerns interpretation of XAS experiments on the basis of the XMCD sum rules, so it concerns also WG5 experiment. The discussions substantially contributed to conclusions which form the basis of a common publication of the grantee and the host. The STSM gave further insight into the interrelation of the impact of spin-orbit coupling on the electronic structure and spectroscopy.

Nuno Silva

Univ Aveiro, PT

Alessandro Lascialfari

Univ. degli studi di Milano, IT

Development of Nanobeads for hyperthermial Thermometry Imaging

The STSM was focused on the interface between COST Actions EUSpec and Radiomag, aiming at the development and validation of nanobeads that work simultaneously as local thermometers exploring a given spectroscopic property and contrast agents in nuclear resonance techniques. This way it contributed to EUSpec WG5: Experiment. The results guided the development of a second generation of nanobeads that will hopefully fulfil the aim of this study, making it ready to dissemination within EUSpec and to the scientific community.

Wilayat Khan

NTC Plzen, CZ

Frank de Groot

Inorganic Chemistry and Catalysis Utrecht, NL

Use of the program package CMT4XAS

During the scientific visit the electronic and spectroscopic properties perovskite FeTiO3, which is proposed to be promising photo-anodes for solar cells, has been studied within a joined project. Atomic multiplet as well as one-electron calculations of the XAS and RIXS spectra at L23 edges of Fe have been calculated for this compound. Accordingly the project supplies a very useful comparison of two rather different theoretical approaches to core level spectroscopy and this way contributes to WG1 correlations and WG2 spectroscopy.

Dominik Legut

IT4Innovation Center Tech.Univ. Ostrava, CZ

P. M. Oppeneer

Uppsala University, SE

Magneto-optical effects, ultrafast demagnetizations and core-level spectroscopy employing density functional calculations

The STSM was devoted to optical calculations beyond the single electron framework. This means to a complete as well as partial core-hole description for various materials starting from metals like Gd to highly ordered pyrolytic graphene and graphene. Work was not done only at the deep core-level, but also at shallow levels as for example M2,3 edges of transitional metals. This work that strongly widens the spectrum of available methods contributes mainly to WG2 Spectroscopy and WG1 Correlation.

Saleem Ayaz Khan

NTC Plzen, CZ

Peter Blaha

TU Vienna Inst. Of Materials Chemistry Vienna, AT

Calculations on Fe/Pt low dimensional nanostructures

The purpose was to calculate magnetic properties of Fe wires on or embedded into Pt(111) surfaces at different geometric configurations. Motivation came from x-ray magnetic circular dichroism experiments which recorded unexpectedly low signal.  The topic thus interconnects WG2: Spectroscopy and WG5: Experiment.  The added value consists of interplay between two physical aspects (structural relaxation and magnetic order) and between two electronic structure codes (WIEN2K and SPRKKR).

Sikander Azam

NTC Plzen, CZ

Igor di Marco

Uppsala University, SE

FP-LMTO method as implemented in code RSPt

The aim of this visit was introduce a new user to the RSPt code for electronic structure calculations provided by the host. This included and introduction to the basic concepts of the dynamical mean-field theory (DMFT) and its implementation in RSPt. Applications of the RSPt code have been done on ZnO with various dopants that were treated by means of supercell calculations. With the focus on correlation effects and their treatment by the DMFT method the STSM contributes primarily to WG1 correlations. In particular it widens the experience in using this scheme.

Davide Sangalli

Physics Deparment at the Politecnico di Milano, IT

Pina Romaniello

CNRS, Lab. De Physique Theorique, Univ. Toulouse III, FR

First principles optical properties of semi-conductors: do different methods give the same answer?

During the STSM a theoretical and numerical comparison of two different approaches to the optical properties of semi-conductors, namely, the formalism in terms of the density-density response function and the one in terms of the current-current response function have been performed. This work contributes to WP2 aiming to improve the theoretical description of spectroscopy. The results will interest also the working group WP3 that is dedicated incorporate time-dependence in theoretical spectroscopy. Results of the present STSM have been presented at the discussion meeting on correlation of the GDR-REST project.

Igor di Marco

Uppsala University, SE

Jan Minar

LMU Munich, DE

Angle-resolved spectroscopy of transition metal mono-oxides

The work performed dealt with some technical problems in the recent implementation of the exact diagonalization (ED) approach for dynamical mean-field theory (DMFT) in the SPR-KKR code for electronic structure calculations. Since the exact diagonalization approach is identified as a fundamental tool for a cross comparison between electronic structure codes, model Hamiltonian tools and quantum chemical embedded cluster methods the STMS contributes mainly to the WG1 correlation. The essential steps concerning its implementation that will provide a new functionality to the SPR-KKR package could be made during the STSM. After completion of the implementation the extended code will be available to other users of the SPR-KKR package.

Federica Agostini

MPI for Microstructurphysics Weinberg, DE

Rudolphe Vuilleumier

CNRS. Dept. Chimie Paris, FR

Analysis of the position-dependent mass (PDM) approach to non-adiabatic dynamics and its application in the field of molecular dynamics

During the STSM a code has been developed to perform quantum dynamics simulations involving electronic excited states. The time-dependent Schrödinger equation is solved for model Hamiltonians in one- and two-dimensional cases including two electronic states. The used models offer a simplified representation of charge transfer processes occurring in molecular systems and involving electronic excited states. The code allows to compare exact quantum-mechanical results with an approximate approach, also implemented during the STSM. The approximation is based on a perturbative treatment of electronic excited-state effects, which introduces position-dependent corrections to the nuclear masses. The purpose of the work was to tune different degrees of non-adiabaticity aiming at a systematic investigation of the performance of the perturbative treatment. The nuclear degrees of freedom, both treated quantum mechanically and as classical trajectories, can be propagated taking the position-dependent correction into account. Thus a contribution could be made to the challenging field of time-dependent spectroscopy covered by WG 3.

Maria Montagna

Dept. of Chem. Sapienza Univ. Rome, IT

Debora Scuderi

Lab. De Chimie Physique, Univ. Paris, FR

Experimental and computational characterization of oxidation products of methionine peptides

The combined experimental and theoretical STSM work was devoted to the characterization of oxidation products of methionine peptide. The focus was on the study of cyclic peptides containing methionine oxidized by gamma radiolysis. To perform this study, a combination of experimental approaches, such as mass spectrometry and Infrared Multiple photon dissociation spectroscopy (IRMPD), was used and complemented by computational means such as ab initio calculations. Good agreement between theoretical and experimental results has been found by this work in progress that contributes to WG 2.

Alla Zak

Holon Institute of technology Holon, IL

Sabrina Sartori

Univ. of Oslo, NO

Use of advanced spectroscopy for the investigation of Na-ion batteries as renewable energy storage systems

Within this project the use of inorganic nanotubes (INT) of WS2 and MoS2 as materials for Na-ion batteries (NIB) has been studied. During the scientific stay an appropriate method for the sample preparation has been developed. The collaborative work was very fruitful and important, as both Dr. Alla Zak and Prof. Sabrina Sartori got an opportunity to share their experience in properties and handling of nanotubes, and in the preparation of anodes for Na-ion batteries in “real life”. This work is valuable contribution to WG5: Experiment.

Fabio Iesari

Univ. of Camerino, Physics Dept. Camerino, IT

Didier Sebilleau

Univ de Rennes, FR

Theory of x-ray based spectroscopy, exploit the expertise, develop and improve codes for data analysis

The aim of the STSM was to extend and finalize in collaboration with Dr. Hatada the graphical user interface for the GNXAS suite of programs, used to analyse EXAFS data. This makes the program more accessible to the community and hence contributes to WG4: Platform. The GUI was used at the EUSpec training school and documented in a publication.

Keisuke Hatada

Institute de Physique de Rennes, Univ. de Rennes 1, France

Peter Krueger,

Nanomaterial Science Dept., Chiba University, Japan

Interface between Electronic Structure code and real space Multiple Scattering code

We worked on development of interface ES2MS code which transfers the SCF charge density from Electronic Structure codes to real space Multiple Scattering code. This plan contributes to WG1:correlation, WG2: Spectroscopy, and at the same time it is an important arrangement of WG4:Platform. The result was reported in the Working Group meeting of EUSpec in AIMIS 15 Hands On Course in Pilsen on 26. Feb. 2015

Marcin Sikora

AGH University of Science and Technology, Cracow, PL

Amélie Juhin

Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Paris, FR

New possibilities offered by RIXS-MCD: data interpretation and plans for future experiments

The goal of the mission was to strengthen collaboration on application of 1s2p RIXS-MCD to probe site-selective magnetic properties of transition metal oxides. The discussion was devoted to understanding the origin of the spectral features observed in RIXS-MCD spectra of single crystalline magnetite and Co ferrite. Moreover, the ideas for 1s2p RIXS-MCD experiments at GALAXIES at SOLEIL and possible directions for the development of the evaluation procedures of experimental data were discussed. The mission was a valuable contribution to common activities of WG5 and WG2. It has also led to publication in J. Elec. Spec. Related Phenom. (2018).