Issue 31, 2016

Time-dependent density functional theory beyond Kohn–Sham Slater determinants

Abstract

When running time-dependent density functional theory (TDDFT) calculations for real-time simulations of non-equilibrium dynamics, the user has a choice of initial Kohn–Sham state, and typically a Slater determinant is used. We explore the impact of this choice on the exchange–correlation potential when the physical system begins in a 50 : 50 superposition of the ground and first-excited state of the system. We investigate the possibility of judiciously choosing a Kohn–Sham initial state that minimizes errors when adiabatic functionals are used. We find that if the Kohn–Sham state is chosen to have a configuration matching the one that dominates the interacting state, this can be achieved for a finite time duration for some but not all such choices. When the Kohn–Sham system does not begin in a Slater determinant, we further argue that the conventional splitting of the exchange–correlation potential into exchange and correlation parts has limited value, and instead propose a decomposition into a “single-particle” contribution that we denote vSxc, and a remainder. The single-particle contribution can be readily computed as an explicit orbital-functional, reduces to exchange in the Slater determinant case, and offers an alternative to the adiabatic approximation as a starting point for TDDFT approximations.

Graphical abstract: Time-dependent density functional theory beyond Kohn–Sham Slater determinants

Article information

Article type
Paper
Submitted
01 Feb 2016
Accepted
07 Mar 2016
First published
07 Mar 2016

Phys. Chem. Chem. Phys., 2016,18, 20976-20985

Time-dependent density functional theory beyond Kohn–Sham Slater determinants

J. I. Fuks, S. E. B. Nielsen, M. Ruggenthaler and N. T. Maitra, Phys. Chem. Chem. Phys., 2016, 18, 20976 DOI: 10.1039/C6CP00722H

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