The theoretical study on the potential energy curves for X¹\varSigma⁺, A¹\varPi and C¹\varSigma^- states of SiO molecule

This paper applies the symmetry-adapted-cluster/symmetry-adapted-cluster configuration-interaction (SAC/SAC-CI) method to optimize the structures for X¹\Sigma⁺, A¹\Pi and C¹\Sigma^- states of SiO molecule with the basis sets D95++, 6-311++G and 6-311++G**. Comparing the obtained results with the experiments, it gets the conclusion that the basis set 6-311++G** is most suitable for the optimal structure calculations of X¹\Sigma⁺, A¹\Pi and C¹\Sigma^- states of SiO molecule. The whole potential energy curves for these electronic states are further scanned by using SAC/6-311++G** method for the ground state and SAC-CI/6-311++G** method for the excited states, then use a least square method to fit Murrell--Sorbie functions, at last the spectroscopic constants and force constants are calculated, which are in good agreement with the experimental data.