Filatov Michael, Cremer Dieter
Department of Theoretical Chemistry, Göteborg University, Kemigården 3, S-41296 Göteborg, Sweden.
J Chem Phys. 2005 Jan 22;122(4):44104. doi: 10.1063/1.1839856.
A simple modification of the zeroth-order regular approximation (ZORA) in relativistic theory is suggested to suppress its erroneous gauge dependence to a high level of approximation. The method, coined gauge-independent ZORA (ZORA-GI), can be easily installed in any existing nonrelativistic quantum chemical package by programming simple one-electron matrix elements for the quasirelativistic Hamiltonian. Results of benchmark calculations obtained with ZORA-GI at the Hartree-Fock (HF) and second-order Moller-Plesset perturbation theory (MP2) level for dihalogens X(2) (X=F,Cl,Br,I,At) are in good agreement with the results of four-component relativistic calculations (HF level) and experimental data (MP2 level). ZORA-GI calculations based on MP2 or coupled-cluster theory with single and double perturbations and a perturbative inclusion of triple excitations [CCSD(T)] lead to accurate atomization energies and molecular geometries for the tetroxides of group VIII elements. With ZORA-GI/CCSD(T), an improved estimate for the atomization energy of hassium (Z=108) tetroxide is obtained.
相对论理论中零阶正则近似（ZORA）的一种简单修正方法被提出来，以将其错误的规范依赖性抑制到高阶近似水平。该方法被称为规范无关ZORA（ZORA-GI），通过为拟相对论哈密顿量编写简单的单电子矩阵元程序，可以很容易地安装到任何现有的非相对论量子化学软件包中。在哈特里-福克（HF）和二阶莫勒-普莱塞特微扰理论（MP2）水平下，使用ZORA-GI对二卤化物X₂（X = F、Cl、Br、I、At）进行基准计算的结果，与四分量相对论计算（HF水平）结果和实验数据（MP2水平）吻合良好。基于MP2或含单双微扰及微扰包含三重激发的耦合簇理论[CCSD(T)]的ZORA-GI计算，得出了第VIII族元素四氧化物的精确原子化能和分子几何结构。使用ZORA-GI/CCSD(T)，得到了改进后的锇（Z = 108）四氧化物原子化能估计值。
