HAM/4, an improved Semiempirical MO Method, Based Upon Slater's Shielding Concept

The Hartree-Fock expression for the total energy of a molecule is rearranged by use of the idempotency of density matrices and by the introduction of the Slater atomic shielding concept. The leading terms in the resulting energy expression equal those in HAM/3. This proves that the HAM/3 model constitutes a proper version of Hartree-Fock theory. The "remaining terms" and the detailed form of the leading terms are discussed, since this will be important in a future improved model: HAM/4.