A method of valence-electron-only ab initio calculation with energy decomposition is presented. In this scheme the part of valence-electron-only ab initio calculation is based on the method of the Barthelat's three-parameter atmic pseudopotential, and the part of energy decomposition is based on the analysis proposed by Morokuma and coworkers. Trial calculations for moclecular complexes (H2O)2, (HF)2, and FCl-NH3 are carried out with this method. The results of these computations are in good agreement with those obtained from Morokuma's original method in which all electron ab initio is used. This indicates that the pseudopotential energy decomposition scheme proposed in this paper is able to provide a result of interaction energy and its components and charge components comparable to that from ab initio treatment, while the computation was simplified.

Key words: COMPUTER APPLICATIONS, QUANTUM CHEMISTRY, AB INITIO CALCULATION, MOLECULAR ORBITAL THEORY