Basis set superposition error free self-consistent field method for molecular interaction in multi-component systems: Projection operator formalism

The self-consistent field method for molecular interaction (SCF MI) by Gianinetti, Raimondi, and Tornaghi is extended to multi-component systems. A set of equations are written with projection operators, and the accurate approximate equations are derived. The method is applied to water clusters and to a fluoride anion complex with a water dimer. The calculated interaction energies are compared with those estimated with the counterpoise method, and they converge to smaller values for extensive basis sets. The underestimation of the binding energy results from the omission of the most part of charge transfer contribution in the wave function. (C) 2001 American Institute of Physics.