Developing new and understanding old approximations in TDDFT
Developing new and understanding old approximations in TDDFT
复制标题
在 TDDFT 中开发新的近似值并理解旧的近似值
DOI：
10.1039/d0fd00049c
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发表时间：
2020
影响因子：
3.4
通讯作者：
Maitra, Neepa T.
中科院分区：
文献类型：
--
作者：
Lacombe, Lionel;Maitra, Neepa T.
当一个系统远离基态时，通常在依赖时间的密度泛函理论计算中使用的绝热近似在某些应用中完全失败，而在其他应用中给出定性好的预测，有时甚至是定量的预测。目前还不清楚为什么会这样，并且开发超越绝热近似的实用近似仍然是一个挑战。本文探讨了三种不同的调查方式。首先，精确时变交换相关势的表达式表明，绝热近似的精度与物理系统的自然轨道占位数与Kohn-Sham系统的自然轨道占位数之间的偏差密切相关，我们在一些精确可解的模型系统上探讨了这一点。精确的表达式进一步提出了一条超越绝热近似的途径，在第二部分中，我们讨论了以这种方式发展的一类新提出的依赖于记忆的近似。最后，我们从耦合常数路径积分中导出了精确交换相关势的新表达式。
When a system has evolved far from a ground-state, the adiabatic approximations commonly used in time-dependent density functional theory calculations completely fail in some applications, while giving qualitatively good predictions in others, and sometimes even quantitative predictions. It is not clearly understood why this is so, and developing practical approximations going beyond the adiabatic approximation remains a challenge. This paper explores three different lines of investigation. First, an expression for the exact time-dependent exchange–correlation potential suggests that the accuracy of an adiabatic approximation is intimately related to the deviation between the natural orbital occupation numbers of the physical system and those of the Kohn–Sham system, and we explore this on some exactly-solvable model systems. The exact expression further suggests a path to go beyond the adiabatic approximations, and in the second part we discuss a newly proposed class of memory-dependent approximations developed in this way. Finally, we derive a new expression for the exact exchange–correlation potential from a coupling-constant path integration.