Electronic structure of polyatomic systems determined with first-order correlation orbitals. Coupled cluster calculations on lithium cyanide

First-order correlation orbitals and the coupled cluster method were employed together with an extended Gaussian basis set to evaluate the relative energies of three isomers of lithium cyanide. The most stable linear LiNC structure has an energy 0.75 kcal/mol lower than the T-shape structure and 2.34 kcal/mol lower than the linear LiCN structure. The first result remains in accord with the recently established lower limit of 0.34 kcal/mol.