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Linear response at the 4-component relativistic density-functional level: application to the frequency-dependent dipole polarizability of Hg, AuH and PtH2
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
2005 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 311, no 1-2, 187-201 p.Article in journal (Refereed) Published
Abstract [en]

We report the implementation and application of linear response density-functional theory (DFT) based on the 4-component relativistic Dirac-Coulomb Hamiltonian. The theory is cast in the language of second quantization and is based on the quasienergy formalism (Floquet theory), replacing the initial state dependence of the Runge-Gross theorem by periodic boundary conditions. Contradictions in causality and symmetry of the time arguments are thereby avoided and the exchange-correlation potential and kernel can be expressed as functional derivatives of the quasienergy. We critically review the derivation of the quasienergy analogues of the Hohenberg-Kohn theorem and the Kohn-Sham formalism and discuss the nature of the quasienergy exchange-correlation functional. Structure is imposed on the response equations in terms of Hermiticity and time-reversal symmetry. It is observed that functionals of spin and current densities, corresponding to time-antisymmetric operators, contribute to frequency-dependent and not static electric properties. Physically, this follows from the fact that only a time-dependent electric field creates a magnetic field. It is furthermore observed that hybrid functionals enhance spin polarization since only exact exchange contributes to anti-Hermitian trial vectors. We apply 4-component relativistic linear response DFT to the calculation of the frequency-dependent polarizability of the iso-electronic series Hg, AuH and PtH2. Unlike for the molecules, the effect of electron correlation on the polarizability of the mercury atom is very large, about 25%. We observe a remarkable performance of the local-density approximation (LDA) functional in reproducing the experimental frequency-dependent polarizability of this atom, clearly superior to that of the BLYP and B3LYP functionals. This allows us to extract Cauchy moments (S(-4) = 382.82 and S(-6) = 6090.89 a.u.) that we believe are superior to experiment since we go to higher order in the Cauchy moment expansion.

Place, publisher, year, edition, pages
2005. Vol. 311, no 1-2, 187-201 p.
Keyword [en]
exchange-correlation functionals, ab-initio methods, kohn-sham theory, perturbation-theory, electric properties, spin-density, molecular polarizabilities, floquet formulation, dirac-equation, local-density
URN: urn:nbn:se:kth:diva-14588DOI: 10.1016/j.chemphys.2004.10.011ISI: 000227514600022OAI: diva2:332629
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-07-13Bibliographically approved

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Salek, Pawel
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Theoretical Chemistry (closed 20110512)
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