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
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.
Example 4.22 Input for a dual-basis B3LYP single-point calculation.
$molecule 0 1 H H 1 0.75 $end $rem METHOD b3lyp BASIS 6-31G* BASIS2 r64G DUAL_BASIS_ENERGY true $end
Example 4.23 Input for a dual-basis B3LYP single-point calculation with a minimal 6-4G small basis.
$molecule 0 1 H H 1 0.75 $end $rem JOBTYPE opt METHOD rimp2 AUX_BASIS rimp2-aug-cc-pVDZ BASIS aug-cc-pVDZ BASIS2 racc-pVDZ DUAL_BASIS_ENERGY true $end
Example 4.24 Input for a dual-basis RI-MP2 geometry optimization.
$molecule 0 1 H H 1 0.75 $end $rem JOBTYPE opt METHOD rimp2 AUX_BASIS rimp2-aug-cc-pVDZ BASIS aug-cc-pVDZ BASIS2 racc-pVDZ DUAL_BASIS_ENERGY true $end
Example 4.25 Input for a dual-basis RI-MP2 single-point calculation with mixed basis sets.
$molecule 0 1 H O 1 1.1 H 2 1.1 1 104.5 $end $rem JOBTYPE opt METHOD rimp2 AUX_BASIS aux_mixed BASIS mixed BASIS2 basis2_mixed DUAL_BASIS_ENERGY true $end $basis H 1 cc-pVTZ **** O 2 aug-cc-pVTZ **** H 3 cc-pVTZ **** $end $basis2 H 1 rcc-pVTZ **** O 2 racc-pVTZ **** H 3 rcc-pVTZ **** $end $aux_basis H 1 rimp2-cc-pVTZ **** O 2 rimp2-aug-cc-pVTZ **** H 3 rimp2-cc-pVTZ **** $end