On the Correlation Problem in Atomic and Molecular Systems. Calculation of Wavefunction Components in Ursellhyphen;Type Expansion Using Quantumhyphen;Field Theoretical Methods

摘要

A method is suggested for the calculation of the matrix elements of the logarithm of an operator which gives the exact wavefunction when operating on the wavefunction in the onehyphen;electron approximation. The method is based on the use of the creation and annihilation operators, holemdash;particle formalism, Wick's theorem, and the technique of Feynmanhyphen;like diagrams. The connection of this method with the configurationhyphen;interaction method as well as with the perturbation theory in the quantumhyphen;field theoretical form is discussed. The method is applied to the simple models of nitrogen and benzene molecules. The results are compared with those obtained with the configurationhyphen;interaction method considering all possible configurations within the chosen basis of onehyphen;electron functions.