TDDFT from molecules to solids: The role of long-range interactions

Classical Hartree effects contribute substantially to the success of time-dependent density functional theory, especially in finite systems. Moreover, exchange-correlation contributions have an asymptotic Coulomb tail similar to the Hartree term, and turn out to be crucial in describing response properties of solids. In this work, we analyze in detail the role of the long-range part of the Coulomb potential in the dielectric response of finite and infinite systems, and elucidate its importance in distinguishing between optical and electron energy loss spectra (in the long wavelength limit q--0). We illustrate numerically and analytically how the imaginary part of the dielectric function and the loss function coincide for finite systems, and how they start to show differences as the distance between objects in an infinite array is decreased (which simulates the formation of a solid). We discuss calculations for the model case of a set of interacting and noninteracting beryllium atoms, as well as for various realistic systems, ranging from molecules to solids, and for complex systems, such as superlattices, nanotubes, nanowires, and nanoclusters.This work was funded in part by the EU’s RTN NANOPHASE, the EU’s 6th Framework Programme through the NANOQUANTA Network of Excellence (NMP4-CT-2004-500198), the French “Ministère de la recherche” in the framework of the “ACI Nanostructures,” Spanish DGES, Basque Country University, and Iberdrola S.A. The work of L. K. D. was funded by the joint research program “ISMIR” between CEA and CNRS. Calculations have been done using ABINIT (http://www.abinit.org/), PWSCF (http://www.pwscf.org/), LSI-CP, and LSI-DP (http://theory.polytechnique.fr/codes/). Computer time was granted by IDRIS (project 000544) and by CEA/DSM on the cluster of Compaq Alphaserver (project p543) and NEC SX6 (project p93). A. R. acknowledges support from the Salvador Madariaga program of the Ministry of Science and Education of Spain for a sabbatical leave at the Ecole Polytechnique where this work was started.Peer reviewe

TDDFT from molecules to solids: The role of long-range interactions

International audienceClassical Hartree effects contribute substantially to the success of time-dependent density functional theory, especially in finite systems. Moreover, exchange-correlation contributions have an asymptotic Coulomb tail similar to the Hartree term, and turn out to be crucial in describing response properties of solids. In this work, we analyze in detail the role of the long-range part of the Coulomb potential in the dielectric response of finite and infinite systems, and elucidate its importance in distinguishing between optical and electron energy loss spectra (in the long wavelength limit q 0). We illustrate numerically and analytically how the imaginary part of the dielectric function and the loss function coincide for finite systems, and how they start to show differences as the distance between objects in an infinite array is decreased (which simulates the formation of a solid). We discuss calculations for the model case of a set of interacting and noninteracting beryllium atoms, as well as for various realistic systems, ranging from molecules to solids, and for complex systems, such as superlattices, nanotubes, nanowires, and nanoclusters