Approach to estimate correlation energies of MNO3 (M=Li, Na, K) molecules

According to the pair correlation energy results of MNO3 (M=Li, Na, K) at MP2-OPT2/6-311++G(d) level with Meld program and the transferability of pair correlation energies of Mδ+ and NO3δ− in MNO3 molecules, a simple approach to estimate correlation energy of MNO3 is reported which can save a lot of computation time. The total correlation energy of MNO3 at MP2(full)/6-311++G(d) and MP2(full)/6-311++G(3df, 3pd) levels by Gaussian 94 procedure are also given in order to compare with those of Meld results and to discuss the influence of basis set size both on the calculation of correlation energy and on the presented simple approach.