发展动量分辨的含时密度泛函理论,实时模拟石墨烯纳米带的激发态

实时的密度泛函理论 (real-time Time Dependent Density Functional Theory,或称 rt-TDDFT) 是基于含时 Kohn-Sham 方程,从实空间实时模拟体系激发态性质的第一性原理计算方法。本文介绍如何利用自主开发的动量分辨的含时密度泛函理论计算方法和软件 Time Dependent ab initio Package (TDAP),研究具有较大尺寸的石墨烯纳米体系的激发态性质。以石墨烯扶手椅型纳米带 (Armchair graphenenanoribbons,AGNRs) 为例,通过直接模拟外加光场下多电子体系的波函数实时演化,得到了体系的光吸收谱以及激发态的动力学过程。这样的计算方法大大提高了周期性体系的计算效率,且不再受微扰论的限制,实现了对大规模、真实体系的动力学性质的实时模拟。

Momentum-Resolved rt-TDDFT Algorithm for Modeling Electronic Excitation in Graphene Nanoribbons

Real-time (rt) time dependent density functional theory (TDDFT) is an efficient ab initio method to study electronic dynamics in real time and real electron-nuclear space. The method is based on time dependent evolution of Kohn-Sham (TDKS) orbitals. Here we report first-principles simulations on electronic excitation dynamics in grapheme nanoribbons (AGNRs) using our home-built Time Dependent ab initio Package (TDAP). We obtain optical absorption spectrum and electron energy loss spectrum (EELS) via applying an external field to AGNRs and then analyze the dynamic evolution of electronic excited states. This algorithm represents an effective way to simulate electronic excitations in periodic systems beyond the limit of perturbation theory.