The application of strictly localized geminals to the description of chemical bonds

Abstract

AbstractA theory is developed in which closed‐shell molecules are viewed as systems of weakly interacting chemical bonds. Composite‐particle creation operators obtained by an appropriate quasiparticle transformation are used to create the wave function of two‐electron bonds. These quasiparticles are bosons, since they are composed of two electrons, but the total many‐electron wave function is properly antisymmetric. The internal structure of the quasi‐Bose‐particles is affected by inductive interbond interactions. Delocalization and dispersion interactions between different bonds are neglected, thus the approach corresponds to a first‐order many‐body PT (Perturbation Theory) with a correlated, but fully localized, reference state. The whole formalism is developed ab initio. The nonorthogonality problem is handled by a biorthogonal formulation. To illustrate the effectiveness of the model, numerical calculations are reported.