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Journal Article

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

##### Locator

http://dx.doi.org/10.1039/C6CP00722H

(Publisher version)

https://arxiv.org/abs/1603.01176

(Preprint)

##### Fulltext (public)

1603.01176v2.pdf

(Preprint), 782KB

##### Supplementary Material (public)

There is no public supplementary material available

##### Citation

Fuks, J. I., Nielsen, S. E. B., Ruggenthaler, M., & Maitra, N. T. (2016). Time-dependent
density functional theory beyond Kohn–Sham Slater determinants.* Physical Chemistry Chemical Physics,*
*18*(31), 20976-20985. doi:10.1039/C6CP00722H.

Cite as: http://hdl.handle.net/11858/00-001M-0000-002B-2083-8

##### 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 v

^{S}_{xc}, 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.