Institut für Physikalische Chemie, Universität Mainz, D-55099 Mainz, Germany.
J Phys Chem A. 2009 Oct 29;113(43):11541-9. doi: 10.1021/jp9028535.
A scheme for the calculation of the electronic g-tensor at the coupled cluster (CC) level is presented. The reported implementation employs an effective one-electron spin-orbit operator, allows the inclusion of arbitrary excitations in the cluster operator, and offers various options concerning the treatment of orbital relaxation and choice of reference determinants. In addition, the use of gauge-including atomic orbitals (GIAOs) is possible to overcome the gauge origin problem. Benchmark calculations for the NH ((3)Sigma(-)) radical reveal the importance of electron correlation effects for the accurate prediction of the g-shift as well as the slow basis set convergence of such calculations, which is only marginally improved by using GIAOs. CC singles and doubles results for the g-tensor are furthermore used to validate various functionals often used in density functional theory calculations. At least for radicals containing only light elements, the B3LYP hybrid functional appears to be the best among the four functionals tested in the present work.
提出了一种在耦合簇（CC）水平上计算电子 g-张量的方案。所报告的实现使用有效的单电子自旋轨道算符，允许在簇算符中包含任意激发，并且提供了关于轨道弛豫处理和参考行列式选择的各种选项。此外，使用包含自洽场（GIAO）的原子轨道是可能的，以克服规范原点问题。对于 NH((3)Sigma(-))自由基的基准计算表明，电子相关效应对准确预测 g-位移以及此类计算的基组收敛速度非常重要，而使用 GIAO 只能略微改善这种情况。g-张量的 CC 单激发和双激发结果进一步用于验证密度泛函理论计算中常用的各种泛函。至少对于仅包含轻元素的自由基，在本工作中测试的四种泛函中，B3LYP 混合泛函似乎是最好的。
