MOLPRO

16 THE SCF PROGRAM 99
MAXIT=maxit Maximum number of iterations (default 60)
SHIFTA|SHIFTC=shifta
SHIFTB|SHIFTO=shiftb
Level shift for closed-shell orbitals in RHF (default −0.3) and
α-spin orbitals in UHF (default 0).
Level shift for open-shell orbitals in RHF and β-spin orbitals
in UHF (default 0)
NITORD|NITORDER]=nitord In open-shell calculations, the orbitals are reordered after each
iteration to obtain maximum overlap with the orbitals from the
previous iteration. This takes only effect after nitord iterations.
The default is depends on the quality of the starting guess.
NITSH|NITSHIFT=nitsh
NITCL|NITCLOSED=nitcl
NITOCC=nitocc
NITORT|NITORTH=nitort
If the iteration count is smaller than nitsh, the shifts are set to
zero. The default depends on the quality of the starting guess.
TORT—
If the iteration count is smaller than nitcl, only the closed-shell
part of the Fock matrix is used (default nitcl= 0).
Starting with iteration nitocc the occupation pattern is kept fixed.
The default depends on the quality of the starting guess.
The orbitals are reorthonormalized after every nitort iterations.
The default is nitort= 10.
POTFAC=potfac Scale factor for potential energy in first iteration (default 1.0).
Note that in case of a restart the iteration count starts with 3.
16.1.2 Options for the diagonalization method
In calculations with very large basis sets, the diagonalization time becomes a significant fraction
of the total CPU time. This can be reduced using the orbital rotation method as described in R.
Polly, H.-J. Werner, F. R. Manby, and Peter J. Knowles, Mol. Phys. 102, 2311 (2004))
MINROT=minrot
NEXPR=nexpr
DEROT=nexpr
JACOBI=jacobi
If minrot≥ 0, the orbital rotation method is employed. Explicit
diagonalization of the full Fock matrix is performed in the first
minrot iterations and in the last iteration. If minrot=0, a default
is used which depends on the starting guess.
Number of terms used in the exponential expansion of the unitary
orbital transformation matrix (default 4).
Energy gap used in the orbital rotation method. For orbitals
within ±derot hartree of the HOMO orbital energy the Fock
matrix is constructed and diagonalized (default 1.0)
If nonzero, use Jacobi diagonalization.
16.1.3 Options for convergence acceleration methods (DIIS)
For more details, see IPOL directive.
IPTYP=iptyp
IPNIT|DIIS START=ipnit
Interpolation type (default DIIS, see IPOL directive).
First iteration for DIIS interpolation.
IPSTEP|DIIS STEP=ipstep Iteration increment for DIIS interpolation.
MAXDIS|MAXDIIS=maxdis
Max number of Fock matrices used in DIIS interpolation (default
10).