Excitons in Solids from Periodic Equation-of-Motion Coupled-Cluster Theory
Excitons in Solids from Periodic Equation-of-Motion Coupled-Cluster Theory
复制标题
从周期运动方程耦合团簇理论研究固体中的激子
DOI：
10.1021/acs.jctc.0c00101
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发表时间：
2020
影响因子：
5.5
通讯作者：
Berkelbach, Timothy C.
中科院分区：
文献类型：
--
作者：
Wang, Xiao;Berkelbach, Timothy C.
本文利用基于高斯的单激发和双激发周期运动方程耦合簇理论（EOM-CCSD）对三维固体的电子激发态进行了从头研究。通过布里渊区采样和动量守恒实现的平移对称的显式使用，可以大大降低成本。我们研究的最大系统使用64k点（4 × 4 × 4网格）对布里渊区进行采样，对应于640个轨道上768个电子的标准EOM-CCSD计算。我们研究了8种简单的主群半导体和绝缘体，它们的直接单线态激发能在3到15 eV之间。与实验值相比，我们预测的激发能平均有符号误差为0.24 eV，平均绝对误差为0.27 eV。虽然该误差与应用于分子的EOM-CCSD的误差相似，但它也可能反映了振动效应的作用，而振动效应在计算中被忽略了。我们的结果支持最近提出的AlP和立方BN的实验光隙修正。我们进一步计算了非零动量激子的能量，并将LiF的激子色散与非弹性x射线散射的实验数据进行了比较。通过计算应变下的激发能，我们提取流体静力变形势来量化激子和声子之间相互作用的强度。我们的研究结果表明，耦合簇理论是精确研究固体中各种激子现象的一种有前途的方法。
We present an ab initio study of electronically excited states of three-dimensional solids using Gaussian-based periodic equation-of-motion coupled-cluster theory with single and double excitations (EOM-CCSD). The explicit use of translational symmetry, as implemented via Brillouin zone sampling and momentum conservation, is responsible for a large reduction in cost. Our largest system studied, which samples the Brillouin zone using 64k-points (a 4 × 4 × 4 mesh), corresponds to a canonical EOM-CCSD calculation of 768 electrons in 640 orbitals. We study eight simple main-group semiconductors and insulators, with direct singlet excitation energies in the range of 3 to 15 eV. Our predicted excitation energies exhibit a mean signed error of 0.24 eV and a mean absolute error of 0.27 eV when compared to experimental values. Although this error is similar to that found for EOM-CCSD applied to molecules, it may also reflect the role of vibrational effects, which are neglected in the calculations. Our results support recently proposed revisions of experimental optical gaps for AlP and cubic BN. We furthermore calculate the energy of excitons with nonzero momentum and compare the exciton dispersion of LiF with experimental data from inelastic X-ray scattering. By calculating excitation energies under strain, we extract hydrostatic deformation potentials to quantify the strength of interactions between excitons and acoustic phonons. Our results indicate that coupled-cluster theory is a promising method for the accurate study of a variety of exciton phenomena in solids.