High level ab initio quantum chemistry in main group studies

Abstract

Quantum mechanical ab inito methods are employed to study molecules contain germa- nium and phosphorus. The dependence of the relative energies of 116 diphosphene and diphosphinylidene compounds on the modification of their structures is studied theoreti- cally. Optimized geometries and relative energies are reported for all structures. In the case of the substitution of both H atoms by lithoxy (OLi) or ONa groups is the diphosphinylidene type structure found to be lower in energy. This result is explained through the natural population analyses, where a very favorable coulombic attraction is found in the OLi sub- stituted diphosphinylidene structure. Next, a theoretical investigation of Ge2CH2 is carried out. The singlet potential energy surface (PES) is systematically explored and energies were obtained using theoretical methods including coupled cluster theory and focal point analy- sis (FPA). Eleven stationary points are located on the Ge2CH2 singlet ground state PES. Among them, seven structures are minima (1S–7S). The global minimum is predicted to be the hydrogen-bridged structure 1S.