Dipole Moment and Electronic Structure Calculations of the Electronic States of the molecular ion SiN+

Karam Hamdan,Ghassan Younes,Mahmoud Korek

doi:10.5539/apr.v8n4p1

Abstract

A theoretical investigation of the lowest electronic states of the molecular ion SiN+ has been performed via Complete Active Space Self Consistent Field (CASSCF) method with Multi Reference Configuration Interaction MRCI+Q (single and double excitations with Davidson correction) calculations. The potential energy curves of the low-lying 37 electronic states in the representation 2s+1Λ(+/-), up to 140000 cm-1 , have been investigated. The permanent dipole moment, the harmonic frequency ωe, the equilibrium internuclear distance Re, the rotational constants Be and the electronic energy with respect to the ground state Te have been calculated for these electronic states. The comparison between the values of the present work and those available in the literature for several electronic states shows a very good agreement. The permanent dipole moment, of the investigated 37 electronic states, have been calculated in the present work for the first time along with the investigation of nine new electronic states that have not been observed yet.

Highlights

The remarkable interest in silicon nitride SiN reside in its important role in the stellar atmosphere and in many properties such as strength, hardness, chemical inertness, good resistance to corrosion, high thermal stability, and good dielectric properties (Katz, 1980)
The permanent dipole moment, the harmonic frequency ωe, the equilibrium internuclear distance Re, the rotational constants Be and the electronic energy with respect to the ground state Te have been calculated for these electronic states
From Complete Active Space Self Consistent Field (CASSCF), CMRCI, CCSDT and density functional theoretical calculations, Cai and François (1999) calculated the spectroscopic constants of the SiN+ molecular ion and they found that the 3Π is 460 cm−1 above the ground state 3Σ- which is in disagreement with the calculated value of Bruna et al (1980)

Summary

Introduction

The remarkable interest in silicon nitride SiN reside in its important role in the stellar atmosphere and in many properties such as strength, hardness, chemical inertness, good resistance to corrosion, high thermal stability, and good dielectric properties (Katz, 1980). By using an ab initio calculation (MRD-CI), Bruna et al (1980) found that the ground state is X3Σ- for this cation. From CASSCF, CMRCI, CCSDT and density functional theoretical calculations, Cai and François (1999) calculated the spectroscopic constants of the SiN+ molecular ion and they found that the 3Π is 460 cm−1 above the ground state 3Σ- which is in disagreement with the calculated value of Bruna et al (1980). Liu et al (2016) investigated the low-lying 10 electronic states with spin orbit interaction of the SiN+ molecular ion by using MRCI+Q calculation. By using a high-level ab initio MRCI+Q calculation, we investigate in the present work, the potential energy curves (PEC’s) for 37 singlet, triplet and quintet electronic states of the SiN+ molecular ion up to 140000 cm-1. Fourteen new electronic states are investigated here for the first time

Method

Potential Energy Curves

Spectroscopic Constants

Conclusion