An accurate many-body expansion potential energy surface for SiH 2 (1 1 A') using a switching function formalism.

An accurate many-body expansion potential energy surface for the ground state of SiH 2 is reported. To warrant the correct behavior at the Si ( 1 D) + H 2 (X 1 Σ+g) dissociation channels involving silicon in the first excited Si ( 1 D) and ground Si ( 3 P) states, a switching function formalism has been utilized. A great deal of ab initio points based on aug-cc-pV(Q+d)Z and aug-cc-pV(5+d)Z basis sets are utilized at the multi-reference configuration interaction level using the full-valence-complete-active-space wave function as the reference. Subsequently the calculated energies are corrected via a many-body expansion method to extrapolate to the complete basis set limit. The topographic features of the novel many-body expansion global potential energy surface are studied in detail, showing a good agreement with the theoretical and experimental results in the literature. Moreover, the integral cross-section of the Si ( 1 D) + H 2 (X 1 Σ+g) → H ( 2 S) + SiH (X 2 Π) reaction has been calculated using the time-dependent wave packet method, which provides support for the reliability of the title potential energy surface. This work can serve as the foundation for the study of Si ( 1 D) + H 2 (X 1 Σ+g) reaction kinetics, and for the construction of the larger multibody expansion potential energy surface of silicon/hydrogen containing systems.