Chemical bond modeling with the energy‐driven orbital localization

Abstract

AbstractThis article concerns the embedding in covalent materials problem in general and the construction of one‐electron pseudoatoms to substitute the parts of a molecule connected with a chemical bond in particular. For this the procedure to part a molecule into the ion‐radicals and bonds within the Hartree–Fock (HF) approach is proposed. In this procedure the ion‐radical occupied orbitals are defined as solutions of HF equations for ion‐radical in the basis of occupied molecular orbitals (MOs) of the whole molecule. The bond orbitals are constructed to complete the functional space span by the occupied MOs of ion‐radicals to the functional space span by occupied MOs of the whole molecule. In this approach it is easy to decompose the total electron density matrix of the whole molecule into the density matrixes of ion‐radicals and bonds. Therefore, the adiabatic potential of the molecule is expressed as a sum of ion‐radical and bonds self‐energies and various intramolecular interaction energies. The equation for the exact bond orbital is developed that is the HF equation for the two‐electron problem in the nonlocal external field and modified Coulomb exchange potential. An approximation for this equation is given. Test calculations were performed for the H2O molecule and the artificial LiOH molecule. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004