4.7 Dual-Basis Self-Consistent Field Calculations

4.7.4 Job Control

Dual-basis calculations are controlled with the following $rem. DUAL_BASIS_ENERGY turns on the dual-basis approximation. Note that use of BASIS2 without DUAL_BASIS_ENERGY only uses basis set projection to generate the initial guess and does not invoke the dual-basis approximation (see Section 4.4.5). OVPROJECTION is used as the default projection mechanism for dual-basis calculations; it is not recommended that this be changed. Specification of SCF variables (e.g., THRESH) will apply to calculations in both basis sets.

DUAL_BASIS_ENERGY
       Activates dual-basis SCF (HF or DFT) energy correction.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       Analytic first derivative available for HF and DFT (see JOBTYPE) Can be used in conjunction with MP2 or RI-MP2 See BASIS, BASIS2, BASISPROJTYPE
RECOMMENDATION:
       Use dual-basis to capture large-basis effects at smaller basis cost. Particularly useful with RI-MP2, in which HF often dominates. Use only proper subsets for small-basis calculation.