MOLE: A system for quantum chemistry. II. recent developments

The concept of a quantum chemical system (QCS) as a viable and useful tool in quantum chemical calculations requires that the system be continuously modified and expanded to handle new developments. The MOLE QCS, as originally conceived, was designed to handle the study of molecular electronic structure by means of the following types of calculations: (1) semiempirical (CNDO/2, Hueckel, extended Hueckel); (2) ab initio SCF; (3) configuration interaction (CI); (4) natural orbital analysis; and (5) expectation values (electronic moments and point properties). Since 1968, MOLE has been continuously modified to improve the efficiency of the algorithms which accomplish the above. Recently major additions have altered MOLE sufficiently to justify reporting its new capabilities. The additions are as follows: (1) extended CI capability; (2) perturbation theory CI for the choosing of optimal configurations; (3) configuration generation capability; (4) improved SCF proficiency; and (5) valence-only electronic structure capability based on the use of model potentials for core electrons. The present paper describes the current status of the MOLE system.