Electronic Structure Models: Computations, Chemical Insights and Appropriateness

Abstract

Electronic structure calculations lie at the very heart of modern theoretical chemistry. We discuss the nature of such calculations, stressing the importance of the central fact that these are model calculations: both ab-initio and semiempirical calculations use electronic structure models, in the form of a representation of the coulomb Hamiltonian over some finite basis set. Different basis sets, with different interaction integrals, correspond to different model Hamiltonians. In this sense, there is no fundamental difference between semiempirical and ab-initio calculations.