Potential energy curves for the X 1 Σ g + B 1 Δ g and B′1 Σ g + states of C2 using MRCI and approximate CI methods

Abstract

The potential energy curves for the X 1 Σ g + , B 1 Δ g and B′1 Σ g + states of C2 have been studied by using MRCI and approximate CI methods, and are benchmarked against the calculations of full configuration interaction (FCI). The results obtained by MRCI method agree with the FCI very well, and even are accurate enough to compare other approximate methods as benchmark, when the calculations of FCI are not feasible. The approximate CI methods mentioned in this paper are reliable for treating chemical problems.