Chamoli Somesh, Surjuse Kshitijkumar, Jangid Bhavnesh, Nayak Malaya K, Dutta Achintya Kumar
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
Theoretical Chemistry Section, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.
J Chem Phys. 2022 May 28;156(20):204120. doi: 10.1063/5.0085932.
We present the theory, implementation, and benchmark results for a frozen natural spinors based reduced cost four-component relativistic coupled cluster method. The natural spinors are obtained by diagonalizing the one-body reduced density matrix from a relativistic second-order Møller-Plesset calculation based on a four-component Dirac-Coulomb Hamiltonian. The correlation energy in the coupled cluster method converges more rapidly with respect to the size of the virtual space in the frozen natural spinor basis than that observed in the standard canonical spinors obtained from the Dirac-Hartree-Fock calculation. The convergence of properties is not smooth in the frozen natural spinor basis. However, the inclusion of the perturbative correction smoothens the convergence of the properties with respect to the size of the virtual space in the frozen natural spinor basis and greatly reduces the truncation errors in both energy and property calculations. The accuracy of the frozen natural spinor based coupled cluster methods can be controlled by a single threshold and is a black box to use.
我们展示了一种基于冻结自然旋量的降低成本的四分量相对论耦合簇方法的理论、实现过程和基准测试结果。自然旋量是通过对基于四分量狄拉克 - 库仑哈密顿量的相对论二阶莫勒 - 普莱塞特计算得到的一体约化密度矩阵进行对角化而获得的。与从狄拉克 - 哈特里 - 福克计算得到的标准正则旋量相比，耦合簇方法中的相关能在冻结自然旋量基下相对于虚拟空间大小的收敛速度更快。在冻结自然旋量基下，性质的收敛并不平滑。然而，包含微扰校正使得在冻结自然旋量基下性质相对于虚拟空间大小的收敛变得平滑，并大大降低了能量和性质计算中的截断误差。基于冻结自然旋量的耦合簇方法的精度可以通过一个单一阈值来控制，并且使用起来是一个黑箱操作。
