Effects on spectroscopic properties for several low-lying electronic states of CS molecule by core-valence correlation and relativistic corrections

► Effect on the PECs by the core-valence correlation and relativistic corrections is considered. ► The PECs obtained by the CCSD(T), MRCI and MRCI + Q are extrapolated to the CBS limit. ► The energy extrapolation scheme obviously improves the quality of spectroscopic parameters. ► The spectroscopic parameters and molecular constants obtained achieve much high accuracy.