MOMENTUM-SPACE AND COULOMB CORRELATION - A 2-PARTICLE DENSITY ANALYSIS FOR THE H-2(1-SIGMA-G+) MOLECULE

Electron correlation in momentum space is assessed for the ground-state of H2 by examining changes in the two-particle probability density evaluated over preselected momentum planes. The associated radial and angular ''planar Coulomb shifts,'' DELTAR(p12) and DELTAA(epsilon(p)), are also calculated. This study complements an earlier analysis for H-2 in position space. The natural expansion of the correlated wave function used previously was converted into momentum space by means of a Dirac-Fourier transform. As before, correlation effects are measured with respect to the description provided by the first natural configuration. Characteristics of the three components of Coulomb correlation for a linear molecule are highlighted by specific choices for the momentum of a ''test'' or ''reference'' electron. Unlike position space, it was found that one component worked in distinct opposition to the other components, a feature analogous to atomic studies in momentum space. The trends observed throughout a series of probability changes in momentum space for H-2 were rationalized and linked to the correlation behavior in position space.