Schweigert Igor V, Bartlett Rodney J
Quantum Theory Project, University of Florida, Gainesville, Florida 32611, USA.
J Chem Phys. 2008 Sep 28;129(12):124109. doi: 10.1063/1.2978171.
Adding a fraction of the nonlocal exchange operator to the local orbital-dependent exchange potential improves the many-body perturbation expansion based on the Kohn-Sham determinant. The effect of such a hybrid scheme on the performance of the orbital-dependent correlation functional from the second-order perturbation theory (PT2H) is investigated numerically. A small fraction of the nonlocal exchange is often sufficient to ensure the existence of the self-consistent solution for the PT2H potential. In the He and Be atoms, including 37% of the nonlocal exchange leads to the correlation energies and electronic densities that are very close to the exact ones. In molecules, varying the fraction of the nonlocal exchange may result in the PT2H energy closely reproducing the CCSD(T) value; however such a fraction depends on the system and does not always result in an accurate electronic density. We also numerically verify that the "semicanonical" perturbation series includes most of the beneficial effects of the nonlocal exchange without sacrificing the locality of the exchange potential.
将非局域交换算符的一部分添加到与局域轨道相关的交换势中，可改进基于Kohn-Sham行列式的多体微扰展开。通过数值研究了这种混合方案对二阶微扰理论（PT2H）中与轨道相关的相关泛函性能的影响。一小部分非局域交换通常足以确保PT2H势自洽解的存在。在氦原子和铍原子中，包含37%的非局域交换会导致相关能和电子密度非常接近精确值。在分子中，改变非局域交换的比例可能会使PT2H能量紧密再现CCSD(T)值；然而，这样的比例取决于系统，并不总是能得到准确的电子密度。我们还通过数值验证了“半正则”微扰级数包含了非局域交换的大部分有益效果，而不会牺牲交换势的局域性。
