Energy continuity in multi-reference CI calculations

Configuration interaction calculations based on changing numbers of reference configurations at different geometries have a theoretical inconsistency which can affect the continuity of a calculated potential surface. As the number of reference configurations is increased for adjacent points on a potential curve (e.g. to describe molecular dissociation), the CI space can increase by large quantum jumps. Using the MRD-CI method of Buenker and Peyerimhoff and coworkers, we give several criteria which help to ensure energy continuity across these changes in CI space, and demonstrate these criteria for the hydrogen fluoride potential curve.

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