Optimized virtual ortibal space for high-level correlated calculations

Ludwik Adamowicz, Rodney J. Bartlett

Research output: Contribution to journalArticlepeer-review

124 Scopus citations


The second order Hylleraas functional and a Newton-Raphson orbital optimization techniquehave been used to generate an active, optimized virtual orbital space (OVOS) of substantially reduced dimension for correlated calculations. Numerical examples for CH2(1A1), C6H6, and potential curves for B2H6 and H2O2 using MBPT and coupled-cluster theory demonstrate that most of the correlation energy can be obtained with a much smaller number of optimized virtual orbitals, and effectively ∼100% of the correlation energy if the OVOS result is combined with the exact second-order energy that is evaluated as a byproduct of the OVOS generation. This suggests a potentially wide applicability of the OVOS method in high accuracy quantum mechanical calculations.

Original languageEnglish (US)
Pages (from-to)6314-6324
Number of pages11
JournalThe Journal of chemical physics
Issue number11
StatePublished - 1987

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry


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