Premium
On the choice and definition of atomic‐orbital bases. I. General considerations; promotion and hybridization; electric dipole moments
Author(s) -
Del Re Giuseppe
Publication year - 1967
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560010308
Subject(s) - slater type orbital , atomic orbital , dipole , molecular orbital , bond dipole moment , molecular orbital theory , orbital hybridisation , basis set , quantum mechanics , electric dipole moment , chemistry , physics , electron configuration , atomic physics , molecule , electron
After a brief discussion of the physical significance of the choice of the basis in molecular calculations, the nature and definition of an atomic‐orbital basis for use in limited calculations is discussed, in view of the possibility of replacing, say, ordinary 2 s and 2 p Slater orbitals by appropriate hybridized‐promoted atomic orbitals. It is indicated that, if the orbitals must be defined in connection with a given interpretation scheme for the behavior of molecules, hybridization and promotion may be necessary. The two kinds of conditions one may wish to impose on a restricted atomic‐orbital set are explicitly considered. The first is that the atomic orbitals should be hybrids directed along the bonds and at the same time satisfy the maximum overlap criterion; the other is the requirement that the atomic orbitals should be such that the electric dipole moment of a polyatomic molecule described in terms of a semiempirical bond‐orbital scheme should be expressed as the dipole moment of the system of bond charges located at the nuclei. The latter condition is treated in detail, showing that it implies a cancellation of atomic and overlap moments. The equations defining the atomic orbitals satisfying the condition in question are given. In the course of the mathematical treatment some general results concerning the expression of the dipole moment of a molecule and the definition of net atomic charges are given, showing that, for systems where overlap integrals are low, the atomic populations can be taken as sums of the squares of the coefficients of orthogonalized atomic orbitals. Applications of the results will be presented in part II.