Fuks Johanna I, Nielsen Søren E B, Ruggenthaler Michael, Maitra Neepa T
Department of Physics and Astronomy, Hunter College and the Graduate Center of the City University of New York, 695 Park Avenue, New York, New York 10065, USA.
Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science & Department of Physics, Luruper Chaussee 149, 22761 Hamburg, Germany and Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21A, A-6020 Innsbruck, Austria.
Phys Chem Chem Phys. 2016 Aug 3;18(31):20976-85. doi: 10.1039/c6cp00722h.
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, 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.
在进行非平衡动力学实时模拟的含时密度泛函理论（TDDFT）计算时，用户可以选择初始的科恩 - 沈（Kohn - Sham）态，通常会使用斯莱特行列式。当物理系统初始处于基态和第一激发态的50 : 50叠加态时，我们探究了这种选择对交换关联势的影响。我们研究了在使用绝热泛函时，明智地选择一个能使误差最小化的科恩 - 沈初始态的可能性。我们发现，如果选择的科恩 - 沈态具有与主导相互作用态的构型相匹配的构型，对于某些但并非所有此类选择，在有限的时间内可以实现这一点。当科恩 - 沈系统不是从斯莱特行列式开始时，我们进一步论证，将交换关联势传统地分解为交换部分和关联部分的价值有限，取而代之的是提出一种分解为我们记为v的“单粒子”贡献和一个余项。单粒子贡献可以很容易地作为显式的轨道泛函来计算，在斯莱特行列式情形下简化为交换项，并且作为TDDFT近似的起点，它提供了一种替代绝热近似的方法。
