MOLPRO

14 INTEGRATION 86
smaller than this value. In DTRAF and DKEXT effective density
matrices are constructed from the MO coefficients and amplitudes,
respectively.
THRINT Integral prescreening threshold. This applies to the product
of the exact (i.e. computed) integral value and a density matrix.
This threshold is only used in DTRAF and DKEXT. A shell
block of integrals is skipped if the product of the largest integral
and the largest element of the effective density matrix
contributing to the shell block is smaller than this threshold. If
it set negative, no computed integrals will be neglected.
THRPROD
THRMAX
SCREEN
MAXRED
VARRED
SWAP
Prescreening threshold for products of integrals and MO-coefficients
(DTRAF) or amplitudes (DKEXT). Shell blocks of MO coefficients
or amplitudes are neglected if the product of the largest
integral in the shell block and the largest coefficient is smaller
than this value. If this is set negative, no product screening is
performed.
Initial value of the prescreening threshold THREST for DFOCK
and DKEXT in iterative methods (SCF, CI, CCSD). If nonzero,
it will also be used for DKEXT in MP3 and MP4(SDQ) calculations.
The threshold will be reduced to THREST once a certain
accuracy has been reached (see VARRED), or latest after
MAXRED iterations. In CI and CCSD calculations, also the initial
thresholds THRINT DKEXT and THRPROD DKEXT are influenced
by this value. For a description, see THRMAX DKEXT.
If THRMAX=0, the final thresholds will be used from the beginning
in all methods.
Enables or disables prescreening.
SCREEN≥ 0: full screening enabled.
SCREEN< 0: THRPROD is unused. No density screening in
direct SCF.
SCREEN< −1: THRINT is unused.
SCREEN< −2: THREST is unused.
Maximum number of iterations after which thresholds are reduced
to their final values in CI and CCSD calculations. If
MAXRED=0, the final thresholds will be used in CI and CCSD
from the beginning (same as THRMAX=0, but MAXRED has no
effect on DSCF. In the latter case a fixed value of 10 is used.
Thresholds are reduced to their final values if the sum of squared
amplitude changes is smaller than this value.
Enables or disables label swapping in SEWARD. Test purpose
only.
Specific options for direct SCF (DFOCK):
THREST DSCF
THRMAX DSCF
Final prescreening threshold in direct SCF. If given, it replaces
the value of THREST.
Initial prescreening threshold in direct SCF. This is used for
the first 7-10 iterations. Once a certain accuracy is reached, the
threshold is reduced to THREST DSCF