Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
Institute of Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
J Chem Phys. 2017 Oct 28;147(16):164101. doi: 10.1063/1.4998815.
Ab initio calculations of crystal field splittings and magnetic properties of lanthanide complexes are usually performed using state-averaged complete active space self-consistent field (CASSCF) calculations and a subsequent spin-orbit calculation mixing the CASSCF wave functions (CASSCF/state interaction with spin-orbit coupling). Because this approach becomes very time-consuming for large molecules, simplifications have been proposed in the literature to determine the state-averaged orbitals by configuration-averaged Hartree-Fock (CAHF) instead of CASSCF. We present an approach which is an extension of the CAHF method. We combine the techniques of local density fitting with CAHF and achieve a significant speedup compared to CASSCF without loss in accuracy. To assess the performance of our method, we apply it to three well-known molecules, namely, Er[N(SiMe)], Er(trensal), and the double-decker (NBu) [Er(Pc)].
从头算方法通常用于计算镧系配合物的晶体场分裂和磁性，该方法采用了平均态完全活性空间自洽场（CASSCF）计算和随后的自旋轨道计算混合 CASSCF 波函数（CASSCF/态相互作用与自旋轨道耦合）。由于这种方法对于大分子来说非常耗时，因此文献中提出了一些简化方法，即用组态平均 Hartree-Fock（CAHF）代替 CASSCF 来确定平均态轨道。我们提出了一种扩展的 CAHF 方法。我们将局部密度拟合技术与 CAHF 相结合，与 CASSCF 相比，在不损失准确性的情况下显著提高了速度。为了评估我们方法的性能，我们将其应用于三个著名的分子，即 Er[N(SiMe)]、Er(trensal)和双层（NBu）[Er(Pc)]。
