32.6 Options

SAPT_LEVEL

Set to 1 for first-order terms ( $E_\mathrm{pol}^{(1)}$ and $E_\mathrm{exch}^{(1)}$), to 2 for additional second order (exchange-)induction terms ( $E_\mathrm{ind}^{(2)}$ and $E_\mathrm{exch-ind}^{(2)}$) and 3 for all first- and second-order terms (including then also $E_\mathrm{disp}^{(2)}$ and $E_\mathrm{exch-disp}^{(2)}$) (default 3)

SAPT_FITLEVEL

Level of density fitting approximations in SAPT which can have values 0 to 3 (default 0)

SAPT_ICPKS

Switch between iterative (=1) and non-iterative (=0) solution of coupled-perturbed Kohn-Sham equations (default 0)

SAPT_CPKSTHR

Threshold for density matrix convergency in the coupled-perturbed Kohn-Sham program (default 1.d-6).

SAPT_CPKMAXIT

Maximum number of iterations in the coupled-perturbed Kohn-Sham program (default 50).

SAPT_FROZENA

Number of frozen electrons in the response calculations for monomer A (default 0)

The following parameters are of importance if SAPT_FITLEVEL$>$0:

SAPT_NFRQ_DISP

Number of frequencies for the Casimir-Polder integration (default 12)

SAPT_NORM_DISP

Norm for the density fitting which can be either COULOMB or NATURAL (default COULOMB)

SAPT_DISP_N4

Can speedup the calculation of the dispersion energy by $N^4$ scaling (default 1)

THR_XCKERN

Density threshold for the xc kernel matrix elements (default 1.d-8)

FIT_XCKERN

Fit both sides of the xc kernel (default 0)

SAPT_DISK

If 0 write all dimer amplitudes to file, if 1 write 3-index response propagators to file and if 2 write 3-index response propagators compressed to file. The latter two variants save disk space but need more CPU time to compute $E^{(2)}_\mathrm{exch-disp}$ (default 0)

COMPRESS_THR

If SAPT_DISK=2 this value determines the compression cutoff (default 1d-12)

UNCOUPLED

If SAPT_DISK$>$0 calculate also uncoupled (exchange-)dispersion energies (default false)

THRAO

Threshold for AO 3-index integrals (default 1.d-12)

THRMO

Threshold for MO 3-index integrals (default 1.d-8)

THROV

Threshold for AO 2-index integrals (default 1.d-10)

THRPROD

Product threshold for first half transformation (default 1.d-8)

THRSW

Threshold for Schwarz screening (default 1.d-5)

C6

Calculate dispersion coefficients for the two monomers (Note that the full dimer basis set is used in each case and that a closer distance of the monomers can perturb the result).

XCKERN_NBLOCK

number of grid points treated together as a block for (aux$\vert$f$_\mathrm{xc}\vert$occ$\times$virt) integrals (default 128)

CFAC

factor for VWN correlation in ALDA xc-kernel (default 1.d0)

The last threshold values for the 2- and 3-index integrals should not be set higher in density fitting calculations as this can cause lower accuracies in the interaction terms. In addition SAPT knows the following subcommands:

MONOMERA

Stores informations (like number of electrons, etc.) about previous monomer A calculation

MONOMERB

See above

INTERMOL

Starts the SAPT calculation

INTERMOL may have the following subkeywords:

CA

Record number of wave function for monomer A (always needed)

CB

Record number of wave function for monomer B (always needed)

SAPTLEVEL

See above

FITLEVEL

See above

ICPKS

See above

FROZA

See above

FROZB

See above

NLEXFAC

Amount of nonlocal exact exchange in hybrid DFT-SAPT calculations

CPKSTHR

Threshold for density matrix convergency in the coupled-perturbed Kohn-Sham program.

CPKSMAXIT

Maximum number of iterations in the coupled-perturbed Kohn-Sham program.