The Establishment Of The High Precision Potential Energy Surfaces Of SiH₂ System And The Corresponding Dynamics Study

Hydrogenated amorphous silicon is now widely used in solar cell fabrication and has made great progress as thin film field effect tubes in applications such as television cameras,computer memory and flat panel displays.Therefore,the preparation of hydrogenated amorphous silicon and the analysis of infrared spectra to provide accurate configuration information on its thin films has long been a popular research topic.In order to facilitate the analysis of the configuration information of hydrogenated amorphous silicon and to study the Si-H reaction system,it is necessary to study the SiH₂ molecule at the atomic molecular level.In this paper,the exact potential energy surfaces of the ground state(1~1A')and the three lower excited states(1~3A'',1~3A',2~1A')of the SiH₂ system are constructed,mainly by using a many-body expansion,and the corresponding molecular reaction dynamics features are discussed detailedly.For the ground state of SiH₂,the multi-reference configuration interaction method with Davidson correction(MRCI(Q))is adopted to calculate a large number of high-precision ab initio energy points under the aug-cc-p V(X+d)Z(X=Q,5)basis sets and extrapolate them to the complete basis sets limit,and then fit them using the many-body expansion method,thus constructing an accurate potential energy surface for SiH₂,while introducing a switching function solves the transition of the one-body term Si from the ~1D to the ~3P state,ensuring its consistent dissociation behaviors in both the Si(~1D)+H₂(X~1?_g⁺)and H(~2S)+SiH(X~2?)dissociation channels.A detailed comparison of the characteristics of this potential energy surface with data from other literature shows a high degree of agreement.In addition,to check the accuracy of the potential energy surface,the molecular dynamics of the SiH₂ system was calculated on the novel potential energy surface using the quantum time-dependent wave packet method,and the mechanism of the reaction of Si with H₂ was proposed,which is a guideline for the study of the preparation and the analysis of the configuration information for hydrogenated amorphous silicon.To explore the dynamic characteristics of SiH₂ system more systematically,a large number of ab initio energy points were calculated at the aug-cc-p V(X+d)Z(X=Q,5)basis sets using state averaged theory at the MRCI(Q)level,then extrapolated to the limit of complete basis sets,and fitted by the many-body expansion method.Finally,three global adiabatic potential energy surfaces of SiH₂ excited states were constructed.The newly constructed potential energy surfaces are used to study the dissociation mechanism,the linear configuration[H-Si-H]characteristics,the C_2v insertion reaction and the energy minimum reaction path.Finally,the integral cross section for the Si+H₂(v=0,j=0)?H+SiH reaction is calculated using the quasi-classical trajectory method to provide a reference for other theoretical studies on excited state dynamics.