ANALYTIC FIRST-ORDER PROPERTIES FROM EXPLICITLY CORRELATED MANY-BODY PERTURBATION-THEORY AND GAUSSIAN GEMINAL BASIS

Theory of analytic first-order properties is formulated in a basis set independent way using the first-quantized many-body perturbation theo ry. This formulation allows the correlation effects to be described wi th explicitly correlated basis sets. The basis of Gaussian geminals is employed to calculate the second-and third-order correlation correcti ons to the lowest multipole moments of the H-2 and LiH molecules. The same formalism is also utilized to compute the intra-atomic correlatio n contribution to the first-order interaction energy for the helium di mer. The results compare favorably with the literature data obtained u sing the conventional, orbital basis approach. (C) 1998 American Insti tute of Physics.