Date of Award

1989

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Neil R. Kestner

Abstract

It is important to remove the basis set superposition error (BSSE) from the intermolecular potential energy calculations with the counterpoise (CP) correction especially for weak intermolecular interactions. However, it has been still questioned whether the counterpoise (CP) correction overestimates the real BSSE. To answer this question is the purpose of this research. In this study, the overestimation of basis set superposition error (BSSE) by the counterpoise (CP) method has been analyzed by an approach called "localized orbital pair correlation". This approach is able to eliminate the overestimation of basis set superposition error (BSSE) for the second order potential energies. Prototype calculations of various molecular dimers have been performed with different geometry configurations and various basis set functions. All results have shown that with the counterpoise (CP) method the overestimation of basis set superposition error (BSSE) at the second order electron correlation potential energy calculations is small and it decreases rapidly as the interaction separation increases. Fortunately, the overestimation of basis set superposition error (BSSE) around the potential energy minimum distance is small enough so that the calculated potential energy at the second order electron correlation calculations are quite accurate with the full counterpoise (FCP) correction.

Pages

273

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