Electron energy loss and inelastic x-ray scattering cross sections from time-dependent density-functional perturbation theory

Abstract

The Liouville-Lanczos approach to linear-response time-dependent density-functional theory is generalized so as to encompass electron energy loss and inelastic x-ray scattering spectroscopies in periodic solids. The computation of virtual orbitals and the manipulation of large matrices are avoided by adopting a representation of response orbitals borrowed from (time-independent) density functional perturbation theory and a suitable Lanczos recursion scheme. The latter allows the bulk of the numerical work to be performed at any given transferred momentum only once, for a whole extended frequency range. The numerical complexity of the method is thus greatly reduced, making the computation of the loss function over a wide frequency range at any given transferred momentum only slightly more expensive than a single standard ground-state calculation and opening the way to computations for systems of unprecedented size and complexity. Our method is validated on the paradigmatic examples of bulk silicon and aluminum, for which both experimental and theoretical results already exist in the literature.

Keywords

Affiliated Institutions

• Centre National de la Recherche Scientifique FR
• The Abdus Salam International Centre for Theoretical Physics (ICTP) IT
• École Polytechnique FR
• Scuola Internazionale Superiore di Studi Avanzati IT
• École Polytechnique Fédérale de Lausanne CH
• Commissariat à l'Énergie Atomique et aux Énergies Alternatives FR

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