A wavefunction model to chemical bonding

In this paper we give a brief survey on some specific aspects of a wavefunction model for chemical bonding which are connected to or have been motivated in part by the work of the late István Mayer and colleagues. After a brief description of the early wavefunction models as reflected in Mayer's works, naturally leading to electron densities, we discuss localized molecular orbitals, and summarize some of the early initiatives and applications. The concept of the Chemical Hamiltonian, as introduced by Mayer, its extensions and some classical and some more advanced connections will be discussed. The twofold motivating role of Mayer in the development of the earliest, ab initio level macromolecular linear scaling methods, giving proven “ab initio quality” protein energy results by the adjustable density matrix assembler method, and in some other molecular fragment advances will be also pointed out. Specific aspects of the wavefunction model for chemical bonding and its quantum mechanical interpretation are discussed. We treat localized molecular orbitals, limits to their transferability and the Chemical Hamiltonian concept. Linear scaling computation of electron correlation as well as macromolecular methods for the calculation of ab initio quality protein energy results are also discussed shortly.