Oakley Meagan S, Gagliardi Laura, Truhlar Donald G
Chemical Theory Center, Department of Chemistry, Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455, USA.
Chicago Center for Theoretical Chemistry, Department of Chemistry, James Franck Institute, Pritzker School of Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA.
Molecules. 2021 May 13;26(10):2881. doi: 10.3390/molecules26102881.
Transition metal silicides are promising materials for improved electronic devices, and this motivates achieving a better understanding of transition metal bonds to silicon. Here we model the ground and excited state bond dissociations of VSi, NbSi, and TaSi using a complete active space (CAS) wave function and a separated-pair (SP) wave function combined with two post-self-consistent field techniques: complete active space with perturbation theory at second order and multiconfiguration pair-density functional theory. The SP approximation is a multiconfiguration self-consistent field method with a selection of configurations based on generalized valence bond theory without the perfect pairing approximation. For both CAS and SP, the active-space composition corresponds to the nominal correlated-participating-orbital scheme. The ground state and low-lying excited states are explored to predict the state ordering for each molecule, and potential energy curves are calculated for the ground state to compare to experiment. The experimental bond dissociation energies of the three diatomic molecules are predicted with eight on-top pair-density functionals with a typical error of 0.2 eV for a CAS wave function and a typical error of 0.3 eV for the SP approximation. We also provide a survey of the accuracy achieved by the SP and extended separated-pair approximations for a broader set of 25 transition metal-ligand bond dissociation energies.
过渡金属硅化物是有望用于改进电子器件的材料，这促使人们更好地理解过渡金属与硅之间的键合。在这里，我们使用完全活性空间（CAS）波函数和分离对（SP）波函数，并结合两种后自洽场技术：二阶微扰理论的完全活性空间和多组态对密度泛函理论，对VSi、NbSi和TaSi的基态和激发态键解离进行建模。SP近似是一种多组态自洽场方法，其组态选择基于广义价键理论，没有完全配对近似。对于CAS和SP，活性空间组成对应于名义上的相关参与轨道方案。探索基态和低激发态以预测每个分子中的态序，并计算基态的势能曲线以与实验进行比较。使用八种顶级对密度泛函预测了这三个双原子分子的实验键解离能，对于CAS波函数，典型误差为0.2 eV，对于SP近似，典型误差为0.3 eV。我们还对更广泛的25种过渡金属-配体键解离能集，给出了SP和扩展分离对近似所达到的精度的综述。
