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CFOUR_ABCDTYPEΒΆ

Specifies the way the \langle ab||cd \rangle molecular orbital integrals are handled in post-MP2 calculations. STANDARD (= 0) uses directly the corresponding MO integrals and thus results in an algorithm which in particular for large-scale calculations results in excessive use of disk space (storage of all \langle ab||cd\rangle integrals. AOBASIS (=2) uses an AO-based algorithm to evaluate all terms involving the \langle ab||cd\rangle integrals and significantly reduces the amount of disk storage. The use of ABCDTYPE=AOBASIS is strongly recommended for all CC calculations up to CCSD(T) and has been implemented for energy, gradient, second-derivative, and excitation energy calculations.

  • Type: string
  • Possible Values: STANDARD, AOBASIS
  • Default: STANDARD