systems, NSD and HCH recover static correlation more rapidly in the dissociation regime, whereas VCH remains inefficient across all determinant counts. The present results, obtained in the STO-6G basis for small benchmark systems, are intended as a controlled methodological study of determinant ordering strategies rather than a comprehensive performance assessment. The ehCI framework provides a practical way to analyze how excitation and seniority interact and to design compact CI expansions.
Lokhande et al. (2026) studied this question.