Hermitian fock matrix in the chemical Hamiltonian approach: Fulfilling Lowdin's prediction

Following a remark of Lowdin, a technique is developed permitting one to formulate the BSSE-fee SCF equations of the chemical Hamiltonian approach (CHA) by using a Hermitian Fock matrix. Contrary to the usual CHA practice, the energy is also calculated with the means of the same Fock matrix. This scheme reproduces exactly the CHA-SCF results usually obtained by using a non-Hermitian Fock matrix for computing the orbitals and a conventional Hermitian one for computing the energy. (C) 2002 Wiley Periodicals, Inc. Int.