Analytic second derivatives in closed-shell coupled-cluster theory with spin-orbit coupling.
Analytic second derivatives in closed-shell coupled-cluster theory with spin-orbit coupling.
复制标题
DOI：
10.1063/1.3245954
复制
发表时间：
2009-10
期刊：
影响因子：
--
通讯作者：
Fan Wang;J. Gauss
中科院分区：
文献类型：
--
作者：
Fan Wang;J. Gauss
本文概述了最近提出的两组份耦合团簇方法的能量几何二阶导数理论，该方法使用了包含在后Hartree-Fock处理中的自旋-轨道耦合的相对论有效核势[F. Wang，J. Gauss，and C.货车Wullen，J.Chem.Phys.129，064113（2008）]，并且在耦合簇单和双（CCSD）水平以及在通过三重激发的微扰处理增强的CCSD水平[CCSD（T）]报道了实现。通过计算PtH（2），PbH（2）和HgH（2）的谐波和基频，证明了所开发的解析二阶导数技术的适用性，所需的三次和半对角四次力场通过数值微分的分析评估的二次力常数获得。自旋轨道耦合效应被证明是不可忽略的三个考虑分子，因此需要考虑在高精度预测的情况下。
The theory for geometrical second derivatives of the energy is outlined for the recently suggested two-component coupled-cluster approach using relativistic effective core potentials with spin-orbit coupling included in the post-Hartree-Fock treatment [F. Wang, J. Gauss, and C. van Wullen, J. Chem. Phys. 129, 064113 (2008)], and an implementation is reported at the coupled-cluster singles and doubles (CCSD) level as well as at the CCSD level augmented by a perturbative treatment of triple excitations [CCSD(T)]. The applicability of the developed analytic second-derivative techniques is demonstrated by computing harmonic and fundamental frequencies for PtH(2), PbH(2), and HgH(2) with the required cubic and semidiagonal quartic force fields obtained by numerical differentiation of the analytically evaluated quadratic force constants. Spin-orbit coupling effects are shown to be non-negligible for the three considered molecules and thus need to be considered in the case of high-accuracy predictions.