27.4 Density-fitting LMP2 (DF-LMP2, RI-LMP2)

Density-fitting LMP2 can be performed with standard density or and Poisson fitting basis sets. The present implementation works only without symmetry. The input is as follows:

DF-LMP2,[lmp2 options]

Optionally, a card DFIT can follow on which the following options can be specified (appropriate default values are available):

BASIS_MP2=string

Fitting basis sets, e.g., JKFIT (default) for standard density fitting or DENSITY:POISSON for mixed density/Poisson fitting. These basis sets must have been defined in a previous BASIS block.

THROV=value:

Screening threshold for 2-index integrals of fitting basis.

THRAO=value:

Screening threshold for 3-index integrals in the AO basis.

THRMO=value:

Screening threshold for half-transformed 3-index integrals.

THRSW=value:

Threshold for Schwarz screening.

THRPROD=value:

Product threshold for screening in first half transformation.

SPARSE=value:

If value is on-zero, use sparse algorithm in second-half transformation (default).

LOCFIT=value:

If value=1 use united orbital fitting domains (default). If value=2 use united pair fit domains.

RDOMAUX=value:

Radius for extending the pair fitting domains. Should be nonzero if LOCFIT=2.

KSCEEN=value:

If value=1 use Schwarz screening (linear scaling algorithm).

MINBLK=value:

Minimum AO blocking size.

MAXBLK=value:

Maximum AO blocking size.

MAXFIT=value:

Maximum block size for fitting functions.

MAXBATCH=value:

Blocking size for first half transformation.

RI-MP2 is an alias for the command DF-MP2. At present, expectation values and gradients cannot be computed with DF-MP2.