4.7 Dual-Basis Self-Consistent Field Calculations

4.7.4 Job Control and Example

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.

4.7.4.1 Examples

Example 4.20  Input for a dual-basis B3LYP single-point calculation.

$molecule
   0 1
   H
   H   1   0.75
$end

$rem
   JOBTYPE             sp
   METHOD              b3lyp
   BASIS               6-31G*
   BASIS2              r64G
   DUAL_BASIS_ENERGY   true
$end

Example 4.21  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 4.22  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 4.23  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