GDR REST General Meeting The GDR-REST aims to bring together different communities of theoretical spectroscopy which are/were historically separated, but with the common goal of describing, analysing and possibly predicting the re- sponse properties of a variety of systems (weakly and strongly correlated systems, valence and core electrons, etc.). One of the objectives of REST is also to foster collaborations with the nuclear physics community, which might face similar problems and use similar approches to the condensed matter and quantum chemistry communities. In the spirit of the GDR REST, and along the same line as the first REST general meeting in Roscoff in 2016, the Porquerolles general meeting will be of interdisciplinary nature, in order to establish the state-of- the-art approaches, share knowledge, identify important issues and unresolved problems, and indicate future directions for the different communities. For this reason four main lectures have been scheduled aiming to create a common vocabulary between physicists and chemists as well as experimentalists and theoreticians, and to introduce the participants to the core-electron spectroscopy as well as to spectroscopies beyond the linear regime. Organizers: • Brice Arnaud Institut des Mol´ ecules et Mat´ eriaux du Mans Universit´ e du Maine 72085 Le Mans Cedex 9 [email protected]• Claudio Attaccalite CNRS/ CINaM Campus de Luminy 13288 Marseille [email protected]• Arjan Berger Laboratoire de Chimie et Physique Quantiques IRSAMC, Universit´ e Paul Sabatier 118 Route de Narbonne 31062 Toulouse Cedex 4 [email protected]• Andres Saul CNRS/ CINaM Campus de Luminy 13288 Marseille [email protected]• Eleonora Luppi Laboratoire de Chimie Th´ eorique Sorbonne Universit´ e - CNRS 4 place Jussieu, 75005 Paris [email protected]• Pina Romaniello Laboratoire de Physique Th´ eorique, IRSAMC Universit´ e Paul Sabatier 118 Route de Narbonne 31062 Toulouse Cedex 4 [email protected]• Hans-Christian Weissker CNRS/ CINaM Campus de Luminy 13288 Marseille [email protected]
Transcript
GDR REST General Meeting
The GDR-REST aims to bring together different communities of theoretical spectroscopy which are/werehistorically separated, but with the common goal of describing, analysing and possibly predicting the re-sponse properties of a variety of systems (weakly and strongly correlated systems, valence and core electrons,etc.). One of the objectives of REST is also to foster collaborations with the nuclear physics community,which might face similar problems and use similar approches to the condensed matter and quantum chemistrycommunities.
In the spirit of the GDR REST, and along the same line as the first REST general meeting in Roscoff in2016, the Porquerolles general meeting will be of interdisciplinary nature, in order to establish the state-of-the-art approaches, share knowledge, identify important issues and unresolved problems, and indicate futuredirections for the different communities.
For this reason four main lectures have been scheduled aiming to create a common vocabulary betweenphysicists and chemists as well as experimentalists and theoreticians, and to introduce the participants tothe core-electron spectroscopy as well as to spectroscopies beyond the linear regime.
Organizers:
• Brice ArnaudInstitut des Molecules et Materiaux du MansUniversite du Maine72085 Le Mans Cedex 9
The meeting will take place at the IGESA Center in the heart of Port Cros National Park on the beautifulisland of Porquerolles (http://www.hyeres-tourism.co.uk/en-hyeres/porquerolles).
The IGESA Center (https://www.igesa.fr/vos-vacances/recherche-sejour/reserver-mes-vacances/etablissement/porquerolles/) is an Army institution created in 1872, which has the CNRS as one of itspartners. It is located at walking distance from La Courtade Beach, in Rue de la Douane, Ile de Porquerolles,83400 HYERES.
Meeting, accommodation, and meals will all take place at the IGESA center.
Boat schedulesPorquerolles is accessible only by boat. The departure harbor is La Tour Fondue, from which you have boats aboutevery hour with ticket costs of about 20 e (return). You can check the schedule athttps://www.tlv-tvm.com/horaires-tarifs-horaires-2 (last ferry at 6pm!).
TourismeBesides the meeting, you might want to enjoy yourself going around Porquerolles. Visit the tourisme office (http://www.hyeres-tourism.co.uk/en-hyeres/porquerolles) for good suggestions!
Meal timesMeals are served during the following (strict) times:
Breakfast 7:15–9:15
Lunch 12:15–13:15
Diner 19:15–20:15
SponsorsWe gladly acknowledge the financial support of both the CNRS and the CEA in the framework of the GDR. Inaddtion, we thank the IRSAMC federation in Toulouse for financial support for the meeting in Porquerolles.
9-10 Keynote Speaker: Julien ToulouseComputational methods for electronic excitation energies from the quantum chemistry perspective
10-10:30 Arjan BergerGreen Functions and Self-Consistency : Insights From the Spherium Model
10:30-11:00 Coffe Break
11-11:30 Mark RaysonA Systematically Convergent All-electron DFT Code FALCON
11:30-12 Luigi GenoveseImpact of open boundaries on the analytic structure of the susceptibility : consequences on the com-putational treatment of linear response in molecular systems
12-14 Lunch
14-14:30 Jaakko KoskeloDynamical screening in homogenous electron gas from Bethe-Salpeter equation
14:30-15:00 Arnaud LorinElectron Energy Loss Spectra of silver chloride: an ab initio approach
15-15:30 Coffe Break
15:30-16:00 Igor ReshetnyakFirst principle description of vanadates: electron-hole interaction and thermal effects
16:00-16:30 Brice ArnaudAnharmonic effects in bismuth
16:30-17:00 Schira RomainPlasmonic Response of Small Silver Clusters from TDDFT Calculations
Time for Discussion
Wednesday 23 May
9-10 Keynote Speaker: Luca PerfettiVisualization of electronic motion in quantum Materials
10-10:30 Ivan MaliyovElectronic excitations in the ionic irradiation of materials
10:30-11:00 Coffe Break
11-11:30 Dario RoccaFirst-Principles Engineering of Charged Defects for Two-Dimensional Quantum Technologies
11:30-12 Ruben FerradasElectric and magnetic properties of solids from the current
10-10:30 Aseem Rajan KshirsagarFirst-principles investigation of photo-responsive metal-organic-frameworks for efficient CO2 capture
10:30-11:00 Coffe Break
11-11:30 Ivan DucheminEmbedded many-body perturbation theory
11:30-12 Claudio AttaccaliteInvisible excitons in hexagonal Boron Nitride
12-14 Lunch
14-14:30 Valerie VeniardLinear electro-optic effect in semiconductors: an ab-initio description for the electronic contribution
14:30-15:00 Fabrice CatoireHigh-Order Harmonic Generation in Solids
15-15:30 Coffe Break
15:30-16:30 Discussion: Present & Future of the GDR REST
Friday 25 May
9-10 Keynote Speaker: Mai DinhReal-time approaches in finite electronic systems irradiated by intense laser fields
10-10:30 Eleonora LuppiOn the optimal basis set for electron dynamics in strong laser fields: the case of H2+
10:30-11:00 Coffe Break
11-11:30 Hans-Christian WeisskerAnalysis of electronic modes in metal clusters from delta-kick calculations
11:30-12 Rajarshi Sinha-RoyLocalized Surface-Plasmon Resonance in Noble-Metal Clusters : Ab initio and Classical-Optics Simu-lations
12:00-12:10 Closing remarks
12:10-14:00 Lunch
Departures
Oral Contributions
General Meeting of the GDR REST Keynote Speaker
Computational methods for electronic excitation energies from thequantum chemistry perspective
Julien Toulouse
Laboratoire de Chimie Theorique (LCT), Sorbonne Universite and CNRS, Paris, France
Abstract
I will give an overview of some of the main quantum chemistry computational methods for calculatingelectronic excitation energies of molecular systems:
• Time-dependent methods based on linear-response theory: time- dependent Hartree-Fock (TDHF),time-dependent density-functional theory (TDDFT), ...
• Time-independent methods based on diagonalization: configura- tion interaction (CI), equation-of-motion coupled cluster (EOM- CC),...
• Time-independent methods with orbital optimization: delta self- consistent field (∆-SCF), state-average multiconfiguration self- consistent field (SA-MCSCF), ... Along the way, I will also talk aboutsome of our own recent devel- opments in this topic, namely approaches based on time-dependentquantum Monte Carlo [1], time-dependent range-separated density- functional theory [2], and time-independent range-separated density- functional theory [3, 4, 5].
References:
[1] B. Mussard, E. Coccia, R. Assaraf, M. Otten, C. J. Umrigar, J. Toulouse, Time-dependent linear-response variational Monte Carlo, Advances in Quantum Chemistry Vol. 76, 255 (2018)
[2] E. Rebolini, J. Toulouse, Range-separated time-dependent density- functional theory with a frequency-dependent second-order Bethe- Salpeter correlation kernel, Journal of Chemical Physics 144, 094107(2016)
[3] E. Rebolini, J. Toulouse, A. M. Teale, T. Helgaker, A. Savin, Exci- tation energies along a range-separated adiabatic connection, Jour- nal of Chemical Physics 141, 044123 (2014)
[4] E. Rebolini, J. Toulouse, A. M. Teale, T. Helgaker, A. Savin, Cal- culating excitation energies byextrapolation along adiabatic con- nections, Physical Review A 91, 032519 (2015)
[5] E. Rebolini, A. M. Teale, T. Helgaker, A. Savin, J. Toulouse, Ex- citation energies from Gorling-Levyperturbation theory along the range-separated adiabatic connection, Molecular Physics, to appear,arXiv:1711.08673.
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Oral Presentation General Meeting of the GDR REST
Green Functions and Self-Consistency: Insights From the SpheriumModel
1 Laboratoire de Chimie et Physique Quantiques, Universite de Toulouse, CNRS, UPS, France2 Laboratoire de Physique Theorique, Universite de Toulouse, CNRS, UPS, France.
3 European Theoretical Spectroscopy Facility (ETSF)
Abstract
We report a study [1] of the performance of different variants of Green function methods for the spheriummodel in which two electrons are confined to the surface of a sphere and interact via a long-range Coulomboperator. We show that the spherium model provides a unique paradigm to study electronic correlationeffects from the weakly correlated regime to the strongly correlated regime, since the mathematics aresimple while the physics is rich. We compare perturbative GW, partially self-consistent GW and second-order Green function (GF2) methods for the computation of ionization potentials, electron affinities, energygaps, correlation energies as well as singlet and triplet neutral excitations by solving the Bethe-Salpeterequation (BSE). We discuss the problem of self-screening in GW and show that it can be partially solvedwith a second-order screened exchange correction (SOSEX). We find that, in general, self-consistencydeteriorates the results with respect to those obtained within perturbative approaches with a Hartree-Fockstarting point. Finally, we unveil an important problem of partial self-consistency in GW: in the weaklycorrelated regime, it can produce artificial discontinuities in the self-energy caused by satellite resonanceswith large weights.
Hedin’s pentagon. The red path shows the self-consistent GW process which bypassesthe computation of the vertex function G.
References:
[1] P.-F. Loos, P. Romaniello, and J.A. Berger, arXiv:1803.04234
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General Meeting of the GDR REST Oral Presentation
FALCON: A Systematically Convergent All-electron DFT Code
Mark Rayson
School of Engineering, Newcastle University, NE1 7RU, United Kingdom
Abstract
A novel method for systematically convergent all-electron density functional calculations will be pre-sented. With increasing focus on accuracy benchmarking of DFT codes, robust kernels for automatedmaterials design, simulation kernels that are usable with little technical knowledge, materials under ex-treme conditions, non-local exchange-correlation functionals, magnetic materials, core level spectroscopy,and post Kohn-Sham methods the need for an efficient and systematically convergent all-electron code hasnever been greater. However, as yet, perhaps surprisingly, no such code is routinely available for use orappears in widely used benchmark tables (e.g. [1]). The FALCON project aims to provide an efficientall-electron kernel with the ultimate aim of having only one single convergence parameter to facilitate easeof use and robustness in high throughput computer-aided materials design.
Impact of open boundaries on the analytic structure of thesusceptibility: consequences on the computational treatment of linear
response in molecular systems
Luigi Genovese1, Marco D’Alessandro2
1 L Sim - INAC - CEA Grenoble2 ISM - CNR - Rome
Abstract
A reliable procedure for the analysis of a system within the framework of the linear response shouldinclude the study of the conditions under which numerical convergence of the results can be achieved.Such considerations are important not only for reproducibility of the results among different computercodes employing diverse formalisms, but also in view of providing a deeper understanding on the impactof models’ approximations on the scientific outcomes of the simulation.We discuss these aspects in the context of linear response treatment of molecular systems. By analysingsimple case-studies with a highly complete numerical formalism, we explore the interplay between localityof the perturbed wavefunctions and the numerical convergence of observable quantities. We identify someconvergence indicators and discuss under which regimes they might be employed. This will enable us todraw some considerations on the analytic structure of the linear susceptivity for open systems and on thepotential convergence issues that might arise in a given computational setup.We believe that such discussion could provide useful considerations and perspectives for the design of aeffective approaches for the study of molecular excitations in realistic conditions.
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General Meeting of the GDR REST Oral Presentation
Dynamical screening in homogenous electron gas from Bethe-Salpeterequation
Jaakko Koskelo1,2 , L. Reining1,2 , M. Gatti1,2,3
1Laboratoire des Solides Irradies, Ecole polytechnique, CNRS, CEA, Universite Paris-Saclay, 91128Palaiseau cedex, France
2European Theoretical Spectroscopy Facility (ETSF)3Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette, France
Abstract
There are ongoing efforts to calculate properties of real materials from quantities calculated in modelsystems [1, 2]. This can be done by designing an effective potential for a chosen observable and im-porting it from a model system thanks to a suitable connector. The relevant effective potential can becalculated in the model once for all in order to be imported in various real materials. This calls for acomprehensive characterisation of the model system. In this contribution, we focus on the density-densityresponse func- tion in χ homogenous electron gas (HEG) calculated from the Bethe- Salpeter equation(BSE). We examine the performance of the stan- dard BSE methodology in HEG by comparing to approx-imations from time-dependent density-functional theory. We study a wide range of momentum transfers qand Wigner-Seitz radii r s and look for phenom- ena like the appearance of the so-called ”ghost exciton” [3].
References:
[1] M. Panholzer et al, arXiv:1708.02992[2] M. Vanzini et al, arXiv:1708.02450[3] Y. Takada, Phys. Rev. B 94, 245106 (2016).
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Oral Presentation General Meeting of the GDR REST
Electron Energy Loss Spectra of silver chloride: an ab initio approach
Arnaud Lorin, Matteo Gatti, Lucia Reining, Francesco Sottile
Laboratoire des Solides Irradies, Ecole Polytechnique, CNRS, CEA-DRF-IRAMIS, UniversiteParis-Saclay, 91128 PALAISEAU Cedex, France
Abstract
Silver chloride has been widely used in photographic process, thanks to its sensitivity to visible lightand its capacity to form latent images. It was at the heart of the works of Edmond Becquerel for the pho-tovoltaic effect (the world’s first solar cell) and the first color photographic process[1]. Its photo-reductioncharacteristics are reversible, which makes photochromic lenses possible. More recently, this materialgained interest also as a photocatalyst[2]. In the present work, we have calculated and analyzed the op-tical and dielectric properties of bulk silver chloride from first principles. We report here the calculatedabsorption and Electron Energy Loss spectra for a perfect crystal of Silver chloride. The calculations havebeen carried out within Time Dependent Density Functional Theory using the Adiabatic Local DensityApproximation [3], as implemented in the DP code [4]. We compare our results with recent experimentalspectra obtained by the Centre de Recherche sur la Conservation with which we collaborate on elucidatingthe mechanisms that might explain the color photochromatic images of Edmond Becquerel.
References:
[1] Edmond Becquerel in ”La lumiere, ses causes et ses effets”, (F. Didot freres, fils et Cie (Paris)).
[2] S. Zhang et al. Chem. Eng. Journal 240, 548 (2014); J. Gou et al. J.Ind. Eng. Chem. 59, 99 (2017)
[3] E. Runge, E.K.U. Gross, Phys. Rev. Lett. 52, 997 (1984) and E.K.U. Gross and W. Kohn, Phys.Rev. Lett. 55, 2850 (1985).
[4] The DP code, F.Sottile, L.Reining, V. Olevano. https://etsf.polytechnique.fr/software/Ab_
First principle description of vanadates: electron-hole interaction andthermal effects
Igor Reshetnyak, Julia Wiktor, Francesco Ambrosio, Alfredo Pasquarello
Chaire de Simulation a l’Echelle Atomique (CSEA), Ecole Polytechnique Federale de Lausanne(EPFL), CH-1015 Lausanne, SWITZERLAND
Abstract
Several complex metal oxides have attracted much attention re- cently due to their potential applicationsas photoanodes for water- splitting photochemical cells. In particular, Bismuth vanadate (BiVO 4 ) andcopper vanadate (Cu 2 V 2 O 7 ) have been suggested as promising candidate materials. Though bothof them have optical band-gaps that favor the absorption of a large portion of the visible spectrum,their final photochemical performance is very dissimilar. To under- stand this contrasting behavior, weperformed ab-initio calculations of their absorption spectra within the framework of the Bethe-SalpeterEquation based on the GW approximation to the self-energy, including effects of spin-orbit coupling, nuclearquantum motion and thermal vi- brations. We showed that in the case of copper vanadate, the low-lyingexcitations are strongly bound and thus cannot be used efficiently for water-splitting. At variance, inbismuth vanadate we found the bind- ing energy to be much smaller and thus having a minor effect onthe efficiency. Furthermore, we explored different approaches to combin- ing electron-hole interaction andthermal effects and showed that the correct treatment of both of them is crucial for obtaining quantitativeagreement with experiments.
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Oral Presentation General Meeting of the GDR REST
Anharmonic effects in bismuth
Brice Arnaud
Institut des Molecules et Materiaux du Mans, UMR CNRS 6283, Le Mans universite, 72085 LeMans Cedex
Abstract
The semi-metal bismuth exhibits many fascinating properties, such as giant magnetoresi- tance, ther-moelectricity and large diamagnetism. The possibility to drive bismuth strongly out of equilibrium byan ultrashort laser pulse and especially to launch the A 1g phonon mode has renewed the interest forbismuth[1-3]. The lifetime of phonons can be measured with Raman experiments (frequency domain) orwith time-resolved pump-probe experiments (time domain). Time-resolved experiments show that thelifetime of the A 1g phonon mode strongly depends on the laser pump fluence and coincides with theRaman measurements in the limit of low fluences. Our goal is to explore phonon-phonon interactions inbismuth and especially to compute the lifetime of the coherent A 1g phonon mode. We computed theelastic constants of bismuth using a finite strain approach and the thermal expansion coefficients usingthe quasi-harmonic approximation. We found an overall good agreement with experiments[4]. We alsocomputed the temperature dependence of the A 1g phonon frequency by including the bubble, loop andtadpole Feynman diagrams in the calculation of the phonon self-energy. The temperature dependence ofthe phonon frequency is in good agreement with the Raman experiments. The lifetime of the A 1g phononmode, that can be computed from the imaginary part of the bubble diagram, is also found to be in goodagreement with Raman experiments. The theoretical description of the coherent phonon lifetime[5] in thehigh fluence regime is currently investigated.
References:[1] D.M. Fritz et al, Science 315, 633 (2007).[2] Y. Giret, A. Gelle and B. Arnaud, Phys. Rev. Lett. 106, 155503 (2011).[3] B. Arnaud and Y. Giret, Phys. Rev. Lett. 110, 016405 (2013).[4] B. Arnaud, S. Lebegue and G. Raffy, Physical Review B 93, 094106 (2016)[5] S. Fahy, E. D. Murray, and D. A. Reis, Phys. Rev. B 93, 134308 (2016).
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General Meeting of the GDR REST Oral Presentation
Plasmonic Response of Small Silver Clusters from TDDFT Calculations.
Romain Schira1, Franck Rabilloud1
1 Universite de Lyon, Universite Claude Bernard Lyon 1, CNRS, Institut Lumiere Matiere,Villeurbanne, France
Abstract
The absorption spectra of silver nanoparticles are characterized by a strong response in the UV-visiblerange, usually interpreted in the framework or semi-classical optics in terms of plasmon excitations due tothe s electrons (Mie’s Theory). Time-Dependent Density-Functional Theory (TDDFT) calculations havebeen shown to well reproduce the experimental spectra of metal nanoclusters when using range-separatedhybrid (RSH) functionals [1,2]. This approach gives a description of the plasmon phenomenon from aquantum point of view and allow investigation of optical properties in a size range where classical andsemi-classical approaches are no longer valid.
We have performed TDDFT simulations of the optical properties of Agn (n=20-147) clusters using RSH-type functionals. We will present tools that allow to identify and caracterize plasmonic excitations withinthe TDDFT framework, and we will discuss about the specificity of plasmonic excitations. We will alsoshow that the electronic shell model hold for small silver cluster, and that magic numbers manifest themselfin they optical properties.
Our calculated spectra are compared to very recent experimental data measured on clusters embedded ina rare gas matrix [3], on oxides matrix, or in contact to a oxide surface [4]. In our calculations the maineffects of those matrices over the cluster’s optical response can be successfully take into account, allowingus to reproduced experimental results with unprecedented accuracy. A presentation of the main effectsinduced by oxidation and by of silica matrices over the optical properties of silver cluster will be done.
Absorption spectra of Agn, cluster in Ne matrix (theory in red vs expt in black), withn=35, 58 and 92. Transition density and hole of the main transition of Ag+147.
References:[1] F. Rabilloud, J. Phys. Chem. A 177, 4267 (2013)[2] F. Rabilloud, J. Chem. Phys. 141, 144302 (2014)[3] R. Schira, F. Rabilloud, B. Issendrof, C. Yu, H. Brune, W. Harbich. Submitted[4] T. Lunskens, P. Heister, M. Tgamer, C.A. Walenta, A. Kartouzian, U. Heiz. JPCC. 17, 17503 (2015)
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Keynote Speaker General Meeting of the GDR REST
Visualization of electronic motion in quantum Materials
Luca Perfetti
Laboratoire des Solides Irradies, Ecole polytechnique, CNRS, CEA, Universite Paris-Saclay, 91128Palaiseau cedex, France
Abstract
The combination of advanced spectroscopic tools and ab-initio calculations is an essential step to pre-dict the properties of solid state materials. To this scope, Angle Resolved Photoelectron Spectroscopy(ARPES) is probably the most powerful and direct approach. As a consequence, theorists of the solidstates are often facing the necessity to decipher ARPES data. Within this context, I will review the basicprinciples of the ARPES method and its extension to the time resolved domain. The band structure oflayered semiconductors and Mott insulators will be benchmarked by first principle calculations of the spec-tral function [1]. In the case of correlated systems, a surprisingly simple correction to density functionaltheory reproduces the experimental results with excellent accuracy. The second part of my talk will dealwith time resolved measurements on model systems. The coupling of electronic states to coherent phonons[2] and polar modes is in good agreement with the theoretical estimates of electron-phonon interaction.Finally, I may discuss the challenging problem of a photoinduced phase transition in high temperature su-perconductors. In this case, the evolution of the electronic states provides evidence of pairing fluctuationsthat are beyond mean field theory [3].
References:
[1] C. Martins, B. Lenz, L. Perfetti, V. Brouet, F. Bertran and S. Biermann, Nonlocal Coulomb corre-lations in pure and electron-doped Sr2IrO4: Spectral functions, Fermi surface, and pseudo-gap-likespectral weight distributions from oriented cluster dynamical mean-field theory, Physical ReviewMaterials 2, 032001 (2018).
[2] E. Papalazarou, J. Faure, J. Mauchain, M. Marsi, A. Taleb-Ibrahimi, I. Reshetnyak, A. van Roekeghem,I. Timrov, N. Vast, B. Arnaud, and L. Perfetti, Coherent phonon coupling to individual Bloch statesin photoexcited bismuth, Phys. Rev. Lett. 108, 256808 (2012).
[3] Z. Zhang, C. Piovera, E. Papalazarou, M. Marsi, M. d’Astuto, C. J. Van Der Beek, A. Taleb-Ibrahimiand L. Perfetti, Photoinduced filling of near-nodal gap in Bi2Sr2CaCu2O8+δ, Physical Review B 96,064510 (2017).
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General Meeting of the GDR REST Oral Presentation
Electronic excitations in the ionic irradiation of materials
Ivan Maliyov, Fabien Bruneval, Jean-Paul Crocombette
CEA, SRMP
Abstract
Ionic irradiation damage in condensed matter is central to many technological fields: materials in nu-clear plants of course, but also electronics in space which is subjected to the solar irradiation, and livingmatter treated by radiotherapy to eliminate tumors. For all these subjects, an accurate knowledge of theinteraction between the irradiating ion and the target is crucial. More precisely, this interaction can besplit into two contributions: a classical collision part and a purely quantum mechanical part induced bythe electronic excitations in the target material. The interaction between an irradiating ion and a targetmaterial is characterized by the energy transfer between them, named the stopping power. We aim atcalculating the electronic stopping power from ab initio simulations here. Previously it was seen thatthe Linear Response Time Dependent Density-Functional Theory is in good agreement with experimentfor proton irradiation[1]. However, it predicts a square dependence on the ion charge for the stoppingpower, which is in clear contradiction to experimental observations. To extend simulations to any inci-dent particle (in charge and mass) and to any material, one needs to use the Real-Time Time DependentDensity-Functional Theory (RT-TDDFT). For this purpose, we developed a RT-TDDFT approach basedon the MOLGW code, a DFT and Green’s function Gaussian basis open source project [2]. This imple-mentation has several appealing advantages: the ability to incorporate core electrons, the ease of using themodern hybrid functionals, and the flexibility of the basis set. In order to calculate the time evolution ofa system subjected to a fast moving point charge, we solve numerically the time-dependent Kohn-Shamequations with the time propagator technique combined with a predictor-corrector scheme [3]. We calcu-lated the stopping power of protons in lithium clusters and evaluated their ability to represent the solid.A great care was taken about the basis set convergence and about the effect of the impact parameter. Thecore electron excitations are found to be very important for the electronic stopping power, especially athigh proton velocity. These results were successfully compared to our earlier linear response results for thesolid [1] and to the SRIM reference [4]. Then we performed the stopping power calculations for the He 2+and antiproton projectiles in Li. For these projectiles, the linear response approximation fails, and thenRT-TDDFT is absolutely needed to make ab initio predictions. For He 2+ projectile, both RT-TDDFTand SRIM results are much lower than the linear response electronic stopping power. Concerning the an-tiproton irradiation, RT-TDDFT calculations showed the antiproton stopping power lower than the protonstopping power, which is in agreement with the general experimental observation [5].
References:[1] A. Shukri, F. Bruneval, Phys. Rev. B 93, 035128 (2016).[2] F. Bruneval et al., Comput. Phys. Commun. 208, 149–161 (2016).[3] A. Castro et. al., Chem. Phys. 121, 3425 (2004).[4] J. Ziegler et al., Ion Implantation Press (2008), textbook.[5] W. Barkas et al., Phys. Rev. 101, 778 (1956).
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Oral Presentation General Meeting of the GDR REST
First-Principles Engineering of Charged Defects for Two-DimensionalQuantum Technologies
Dario Rocca1 , Feng Wu2, Ravishankar Sundararaman3 et Yuan Ping2
1 Universite de Lorraine and CNRS, LPCT, UMR 7019, Nancy, , France.2 University of California Santa Cruz, Santa Cruz, California, United States.
Abstract
Charged defects in two-dimensional (2D) materials have emerging applications in quantum technolo-gies such as quantum emitters and quantum computation. The advancement of these technologies requiresa rational design of ideal defect centers, demanding reliable computation methods for the quantitativelyaccurate prediction of defect properties. We present an accurate, parameter-free, and efficient procedureto evaluate the quasiparticle defect states and thermodynamic charge transition levels of defects in 2Dmaterials [1]. Importantly, we solve critical issues that stem from the strongly anisotropic screening in 2Dmaterials, that have so far precluded the accurate prediction of charge transition levels in these materials.Using this procedure, we investigate various defects in monolayer hexagonal boron nitride (h-BN) for theircharge transition levels, stable spin states, and optical excitations. We identify CBVN (nitrogen vacancyadjacent to carbon substitution of boron) to be the most promising defect candidate for scalable quantumbit and emitter applications.
CBNV (a) and NBNV (b) defects in monolayer hexagonal boron nitride.
Electric and magnetic properties of solids from the current density
R. Ferradas1, P. Romaniello2 and J.A. Berger1
1 Laboratoire de Chimie et Physique Quantiques, IRSAMC, Universite de Toulouse, CNRS, UPS,France
2 Laboratoire de Physique Theorique, IRSAMC, Universite de Toulouse, CNRS, UPS, France
Abstract
The evaluation of the macroscopic polarization and magnetization of solids is problematic when periodicboundary conditions are used because surface effects are artificially removed. This poses a problem unlesssurface effects can be reformulated in terms of bulk quantities[1]. In this work we show the advantage ofcalculating electric and magnetic response properties of solids using the current density as basic variable.An efficient approach to calculate the current density is time-dependent current-density-functional theory(TDCDFT). In TDCDFT the electron current-density enters, replacing the electron density of ordinaryTDDFT as the fundamental dynamical variable, with a vector potential instead of a scalar potential asits conjugate variable. We will show results for optical properties of solids using a recently developedfunctional[2]. We will also discuss how the magnetization can be described within this framework.
References:[1] J. Chem. Phys. 112, 6517 ; Phys. Rev. B 71, 155108 (2005)[2] Phys. Rev. Lett. 115, 137402 (2015)
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Keynote Speaker General Meeting of the GDR REST
Core-level spectra modelling
Delphine Cabaret
Sorbonne Universite, Museum National d’Histoire Naturelle, UMR CNRS 7509, IRD, Institut deMineralogie, de Physique des Materiaux et de Cosmochimie, IMPMC, 75005 Paris, France
Abstract
My lecture will deal with the various approaches currently used to model core-level spectra, as mea-sured by X-ray absorption, inelastic X-ray scattering, or electron energy-loss spectroscopy. For all thesespectroscopies, the modelling methods involve the calculation of transition matrix elements from an initialstate to a final state through a Hamiltonian interaction. The most used are: (i) the multiplet theorydedicated to the calculation of spectra involving localized electronic final states, for instance the L2,3
edges of transitions metals [1], (ii) single-particle methods, relying on density functional theory (DFT),particularly well suited to the calculation of spectra corresponding to non-localized electronic final states(for instance all the K-edges) [2]. Besides, approaches mixing both methods have been recently developed[3], as well as beyond-DFT methods [4], based on the Bethe Salpeter-equation, which are widely used invalence spectroscopies.In this talk, though pedagogical examples, I will show how calculations are crucial to interpret and analyseexperimental spectra. The multipole contributions, the angular dependence and the impact of vibrations[5] will be emphasized, and the issue of core-hole-electron interaction modelling will be addressed.
References:
[1] F. de Groot, Coord. Chem. Rev. 249 (2005) 31.
[2] M. Taillefumier, D. Cabaret, A.-M. Flank and F. Mauri Phys. Rev. B 66 (2002) 195107. Ch.Gougoussis, M. Calandra, A.-P. Seitsonen, F. Mauri, Phys. Rev. B 80 (2009) 075102.
[3] M. W. Haverkort, M. Zwierzycki and O. K. Andersen, Phys. Rev. B 85 (2012) 165113.
[4] J. Vinson, J. J. Rehr, J. J. Kas, E. L. Shirley, Phys. Rev. B 83 (2011) 115106.
[5] R. Nemausat, Ch. Gervais, Ch. Brouder, N. Trcera, A. Bordage, C. Coelho-Diogo, A. Rakhmatullin,I. Errea, L. Paulatto, M. Lazzeri and D. Cabaret, Phys. Chem. Chem. Phys. 19 (2017) 6246.
22
General Meeting of the GDR REST Oral Presentation
First-principles investigation of photo-responsivemetal-organic-frameworks for efficent CO2 capture
Aseem Rajan Kshirsagar, Roberta Poloni.
Univ. Grenoble Alpes, CNRS, Grenoble-INP, SIMaP, Grenoble 38000, France
Abstract
Efficient technologies for CO2 capture and its sequestration (CCS) can be vital for mitigating theproblem of climate change arising from increasing CO2 emissions1. Metal-organic frameworks (MOFs)are crystalline solids with high porosity and affinity for CO2, that are attracting significant attention inthe development of efficient carbon capture technologies3. Specifically, the use of photo-responsive MOFscan be effective in reducing the energy costs associated with CCS, since light, instead of temperature orpressure, would be used as the driving force for change in the adsorption of CO2.A MOF functionalized with azobenzene molecules (PCN-123) has been shown to achieve a significantreversible change of CO2 adsorption as a result of the light-induced trans-to-cis isomerization2. Recently,we demonstrated that the underlying mechanism responsible for reversible CO2 adsorption in PCN-123is the steric blocking-unblocking of the metal nodes by azo functionalizations4. The efficiency of suchphotomodulated CCS can be improved by obtaining higher yields of trans and cis configurations, so thatlarger amounts of CO2 are captured at each cycle. We have employed DFT and GW/BSE calculations toaccurately determine the geometries and the absorption spectra of recently synthesized photo-responsiveMOFs. This study would shed light on the role of the MOF on the geometry of azo functional groups andon the S1 and S2 excitations which are directly connected to the photo-stationary state yields of trans andcis.
Left: reversible photo-isomerization of functional group (blue) in PCN-123 MOF caus-ing blocking-unblocking of metal node (violet), right: calculated adsorption isothermshowing reversible change in CO2 uptake.
References:[1] S. Pacala and R. Socolow, Science 305 (2004) 968.[2] J. Park, D. Yuan, et. al. Journal of the American Chemical Society 134 (2011) 126.[3] R. Poloni, B. Smit, J. Neaton, Journal of Physical Chemistry A 116 (2012) 4957.[4] C. Yang, A.C. Eddin, A.R. Kshirsagar, L.C. Lin, R. Poloni (under revision).
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Oral Presentation General Meeting of the GDR REST
Embedded many-body perturbation theory
Ivan Duchemin
LSim laboratory,CEA/UJF, INAC, Grenoble
Abstract
The merging of the GW and Bethe-Salpeter equation (BSE) formalisms with continuous or discretepolarisable models [1,2] allows us to study the electronic and optical properties of molecular systems em-bedded in complex electrostatic and dielectric environments, such as the absolute position with respect tothe vacuum level of the band edges of organic semiconductors under bulk or surface conditions. Combina-tion of BSE with polarisable models allows then to account simultaneously for ”state specific” and ”linearresponse” effects, solving a long standing problem faced by time-dependent DFT calculations. [3] As afirst application, we discuss the mechanisms allowing to understand the doping mechanisms in organicsemiconductors where donor/acceptor levels are in general very deep. [4]
References:
[1] I. Duchemin, D. Jacquemin, X. Blase, J. Chem. Phys. 144, 164106 (2016).
[2] J. Li, G. D’Avino, I. Duchemin, D. Beljonne, X. Blase, J. Phys. Chem. Lett. 7, 2814 (2016).
[3] I. Duchemin, C. A. Guido, D. Jacquemin, X. Blase,Chemical Science, 2018, DOI: 10.1039/C8SC00529J
[4] J. Li, G. D’Avino, A. Pershin, D. Jacquemin, I. Duchemin, D. Beljonne, X. Blase, Phys. Rev.Materials 1, 025602 (2017).
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General Meeting of the GDR REST Oral Presentation
Invisible excitations in hexagonal Boron Nitride
C. Attaccalite1, L. Sponza,2 H. Amara,2 A. Loiseau,2 F. Ducastelle2
1 CNRS/Aix-Marseille Universite - CINaM Campus de Luminy Marseille, France2 LEM UMR 104, ONERA–CNRS, F-92322 Chatillon, France
Abstract
In this talk I will describe excitations in hexagonal boron nitride that are not visible in the opticalresponse. In particular I will focus on electron-loss spectroscopy[1], and show that this technique can re-veal the indirect nature of h-BN. Then I will discuss two-photon absorption as possible tool to probe darkstates below the bright exciton of the h-BN[2]. These states have a strong implication for luminescenceproperties of this material.
Laboratoire des Solides Irradies, Ecole Polytechnique, CNRS, CEA-DRF-IRAMIS, UniversiteParis-Saclay, 91128 PALAISEAU Cedex, France
Abstract
A deep understanding of the nonlinear optical properties of solids is crucial for the improvement ofnonlinear devices and provides an opportunity to search for new materials. Among all the non-linear phe-nomena existing in nature, an important role is played by the electro-optic effect. The electro-optic effectproduces a change of the refractive index in a medium using a DC electric field and has attracted particularinterest for the development of optoelectronic devices. In the linear electro-optic effect (LEO) or Pockelseffect, the change is proportional to the applied electric field. It may be seen as a second-order polarizationand then described by a second-order susceptibility, which is known to be zero in the dipole approximationfor centro- symmetric materials. Therefore a peculiarity of the LEO effect comes from the fact that itonly occurs in materials without inversion symmetry or originates from symmetry-breaking regions. Fromthe theoretical point of view, most of the calculations for second-order susceptibilities have been done inthe framework of Second Harmonic Generation[1]. In that case, the frequency of the incoming field isconsidered as high with respect to vibrational frequencies and the lattice is kept static. Therefore, one hasto evaluate only the electronic contribution, obtained directly from the optical susceptibility, coming fromthe interaction of the valence electrons and the electric fields. The knowledge of the electro-optic tensorimplies in principle the evaluation of two additional contributions, the ionic and piezoelectric parts. Theionic contribution is linked to the ionic displacements and depends on the variation of the dielectric tensorinduced by these displacements. The piezoelectric contribution comes from the possible modification ofthe shape of the unit cell due to the electric forces[2]. We will show our results for the second order sus-ceptibility describing the LEO tensor, within the ab initio framework of time-dependent density-functionaltheory. We will present our analytic derivation of the macroscopic polarization up to second order in termsof the electric fields, including the effect of a scissors operator to account for the quasi-particle effect.Excitonic effects will be included on the basis of a simple approach. These results will be compared withexperimental data, by taking into account explicitly the ionic part through the Faust-Henry coefficient.The validity of this approximation will also be discussed.
Electronic part of the LEO susceptibility for GaAs calculated in this work (green curve)and extracted from the experimental results compiled in [4] (red dots).
References:[1] E. Luppi and V. Veniard, Semiconductor Science and Technology 31, 123002 (2016)[2] M. Veithen, X. Gonze, and P. Ghosez, Phys. Rev. B 71,125107 (2005).
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General Meeting of the GDR REST Oral Presentation
High-Order Harmonic Generation in Solids
Fabrice Catoire, Henri Bachau
Centre des Lasers Intenses et Applications CNRS-CEA-Univsersite de Bordeaux, 351 Cours de laLiberation, Talence F-33405, France
Abstract
High-order Harmonic Generation (HHG) has received a lot of attention since its first production in the90’s in gaz phase. It is now well established that the generation process is qualitatively described using asemi-classical model which leads to the three-step model : i - the target; in gaz phase, releases an electronwave packet after the interaction with the laser ii - the wave packet gains energy under the influence ofthe laser iii - part of the wave packet has a chance to come back in the vicinity of the parent ion and torecombine emitting a photon in the UV-XUV range by energy conservation [1]. Since this process occurs ateach half cycle of the drive laser, the structure of the harmonic spectrum is composed of odd frequencies ofthe fundamental drive laser. The spectrum is build up of two regions: a plateau going from the ionizationthreshold (Ip) to a cut-off energy given by 3.2Up + Ip where Up is the ponderomotive energy. The cut-offregion corresponds to a fast decrease of the yield vs the harmonic order.More recently HHG has been generated in solids [2]. The structure of the spectrum is quite different ascompared to the generation in gaz phases since it is build up of several plateau. The evolution of the cut-offs, which is proportional to the peak intensity of the drive laser for gaz phase, turns out to be proportionalto the peak electric field for the solid counter part. In this work, we will present a theoretical approachwhich leads to the so-called inter- and intraband harmonic processes. We will focus on the scaling laws ofthe cut-off energy, harmonic yield and emission time. In particular, we will emphasize the contribution ofthe intraband process [3], supposedly leading to a stronger signal below the band gap as compared to theinterband process. A Wannier description [4] of the Houston states will be presented as depicted in Fig. 6.
Stark Wannier energy alE
Hopping Dl = 1
Hopping Dl = 2
𝜔𝐵 𝑡 = 𝑎𝐸 𝑡𝑠= 𝑛𝜔0
Emission of harmonic
n at the time ts
2 𝜔𝐵 𝑡 = 2𝑎𝐸 𝑡𝑠2= 𝑛𝜔0
Emission of harmonic
n at the time ts2
Wannier site l
Wannier site l+1
Wannier site l+2
Schematic reprentation of the hopping between Wannier states ∆l, leading to harmonichigh-order generation of energy nω0 at the time ts satisfying the energy conservationωB(ts) = nω0 where ωB is the instantaneous Bloch frequency.
References:
[1] M. Lewenstein, Ph. Balcou, M. Yu Ivanov, A. L’huillier and P.B. Corkum Phys. Rev. A 40 (1994)2117
[2] S. Ghimire, A.D. DiChiara, E. Sistrunk, P. Agostini, L.F. DiMauro and D.A. Reis Nat. Phys. 7(2011) 138
[3] F. Catoire, H. Bachau, Z. Wang, C. Blaga, P. Agostini and L.F. Dimauro Submitted to PRL
[4] G. Wannier Phys. Rev. 52 (1947) 191
27
Keynote Speaker General Meeting of the GDR REST
Real-time approaches in finite electronic systems irradiated by intenselaser fields
Phuong Mai Dinh1 , Cong-Zhang Gao2 , Chris Meier3 , Paul-Gerhard Reinhard4 and Eric Suraud1
1Laboratoire de Physique Theorique de Toulouse, Universite Paul Sabatier, IRSAMC, CNRS,Toulouse, France
2 Institute of Applied Physics and Computational Mathematics, Beijing 100088, China3 Laboratoire Collisions-Agregats-Reactivite, Universite Paul Sabatier, IRSAMC, CNRS, Toulouse,
France4 Institute for Theoretical Physics, University of Erlangen, Germany
Abstract
Electronic emission from molecules and clusters subject to laser fields is of strong current interest aselectrons allow us to investigate the short times dynamics of the coupling of the system to the laser field.With the advent of laser pulses of very high intensity and/or high frequency, or even the use of attopulsetrains, electronic observables as photo-electron spectra constitute a real challenge at the side of the theo-retical description of the dynamical response of the system under such a laser field, far beyond the linearresponse, therefore calling for real-time approaches. In this talk, I will focus on real-time time-dependentmean-field-based methods which consti- tute a tractable solution for the study of relatively large electronicsystems (up to some hun- dreds of electrons) on a relatively long time (some hundreds of femtoseconds).I will in particular present the real-time and real-space TDDFT code developed in our group since morethan two decades with, as the main objective, the theoretical description of electronic emission [1]. I willthen give some examples of applications of this code in the fullerene C 60 for the study of time- resolveddynamics : high harmonic generation by a very intense laser field [2], carrier-phase envelop effects when avery short laser pulse is used [3], and finally a pump-probe study with an IR pulse as the pump and anXUV attotrain as the probe [4].
References:
[1] P.M. Dinh, P.-G. Reinhard, E. Suraud, Phys. Rep. 485 (2010) 43 ; P. Wopperer, P. M. Dinh,Reinhard, E. Suraud, Phys. Rep. 562 (2015) 1.
[2] C.-Z. Gao, P. M. Dinh, P. Kluepfel, C. Meier, P.-G. Reinhard, E. Suraud, Phys. Rev. A 93 (2016)022506
[3] C.-Z. Gao, P. M. Dinh, P.-G. Reinhard, E. Suraud, C. Meier, Phys. Rev. A 95 (2017) 033427
[4] C.-Z. Gao, P. M. Dinh, P.-G. Reinhard, E. Suraud, Phys. Chem. Chem. Phys. 19 (2017) 19784
28
General Meeting of the GDR REST Oral Presentation
On the optimal basis set for electron dynamics in strong laser fields : thecase of H+
Eleonora Luppi
Laboratoire de Chimie Theorique, Sorbonne Universite and CNRS, F-75005 Paris, France.
Abstract
A clear understanding of the mechanisms that control the electron dynamics in strong laser field is stilla challenge that requires to be interpreted by advanced theory. Development of accurate theoretical andcomputational methods, able to provide a precise treatment of the fun- damental processes generated in thestrong field regime, is therefore crucial. A central aspect is the choice of the basis set for the wave functionexpansion. Accuracy in describing multiphoton processes is strictly related to the intrinsic properties of thebasis set, such as numerical conver- gence, computational cost, or representation of the continuum. [1] Byexplicitly solving the 1D and 3D time-dependent Schrodinger equation for H+2 in presence of an intenseelectric field, we explored the numerical performance of real-space grid, B-spline and Gaussian basis setoptimized for the continuum. [2-3] We analyzed the performance of the three basis sets for high-harmonicgeneration and above-threshold ionization for H+2 . In particular, for high-harmonic generation, the ca-pability of the basis set to reproduce the “two-center interferences” is investigated. [4]
References:
[1] E. Luppi and M. Head-Gordon J. Chem. Phys. 139, 164121 (2013).
[2] H. Bachau, E. Cormier, P. Decleva, J. E. Hansenand and F.Martın, Rep. Prog. Phys. 64, 1815-1942(2001).
[3] E. Coccia, B. Mussard, M. Labeye, J. Caillat, R. Taıeb, J. Toulouse and E. Luppi, Int. J. QuantumChem. 166, 1120-1131 (2016).
[4] F. Zapata, M. Labeye, E. Coccia, V. Veniard, J. Toulouse, J. Caillat, R.Taıeb and E. Luppi, inpreparation (2018).
29
Oral Presentation General Meeting of the GDR REST
Analysis of electronic modes in metal clusters from delta-kickcalculations
Rajarshi Sinha-Roy1,2,3 and Hans-Christian Weissker1,3
1Aix Marseille University, CNRS, CINaM UMR 7325, 13288, Marseille, France.2Departamento de Fısıca Teorica de la Materia Condensada and Condensed Matter Physics Center
(IFIMAC), Universidad Autonoma de Madrid, E-28049 Madrid, Spain3European Theoretical Spectroscopy Facility (ETSF).
Abstract
The real-time propagation scheme of Yabana and Bertsch gives direct access to the density dynamicsand related quantities (dipole, absorption spectra...), but the results are relatively difficult to interpret dueto the lack of direct information on the origin of spectral features, as least in comparison with transition-based linear-response calculations. We analyze the time- dependent density from delta-kick time-evolutioncalculations using spatially resolved Fourier transformation, in this way obtaining spatial information aboutthe origin of individual peaks in the spectra. Individual modes can be identified using color maps, and alsorecovered from the Fourier coefficients to obtain animations.
30
General Meeting of the GDR REST Oral Presentation
Localized Surface-Plasmon Resonance in Noble-Metal Clusters: Abinitio and Classical-Optics Simulations
Rajarshi Sinha-Roy1,2,4, Antonio I. Fernandez-Domınguez2, Pablo Garcıa-Gonzalez3,
Hans-Christian Weissker1,4
1 Aix Marseille University, CNRS, CINaM UMR 7325, 13288, Marseille, France.2 Departamento de Fısıca Teorica de la Materia Condensada and Condensed Matter Physics Center
(IFIMAC), Universidad Autonoma de Madrid, E-28049 Madrid, Spain3 Universite Lyon, Universite Claude Bernard Lyon 1, CNRS, Institut Lumiere Matiere, F-69622,
Villeurbanne, France.4 European Theoretical Spectroscopy Facility (ETSF).
Abstract
The fundamental research interest in nanometric pieces of noble metals is mainly due to the localizedsurface-plasmon resonance (LSPR) in the optical absorption. Theoretical research on LSPRs in nanopar-ticles is performed using different levels of theory depending on the size of the nanoparticles. In particular,the transition from larger metallic nanoparticles with smooth electronic bands and optical spectra to smallmolecule-like clusters with their discrete electronic states and spectra reflects the quantum nature of theclusters. In this work different aspects related to the theoretical understanding of LSPRs in ‘intermediate-size’ noble-metal clusters, where this transition is widely noticed, is explored. Both the real-time ab initioformalism of time-dependent density-functional theory (RT-TDDFT) and the classical electromagneticsapproach are employed. A systematic and detailed comparison of these two approaches highlights andquantifies the limitations of the electromagnetics approach when applied to quantum-sized systems [1].The differences between collective plasmonic excitations and the excitations involving d-electrons, as wellas the interplay between them are explored in the spatial behaviour of the corresponding induced densitiesby performing the spatially resolved Fourier analysis of the time-dependent induced density.
References:
[1] Classical and ab Initio Plasmonics Meet at Sub-nanometric Noble Metal Rods. R. Sinha-Roy, P.Garcıa-Gonzalez, H.-Ch. Weissker, F. Rabilloud, A. I. Fernandez-Domınguez. ACS Photonics 2017,4, 1484–1493
