5.13 Methods Based on “Constrained” DFT

5.13.2 Job Control

(June 30, 2021)

A CDFT calculation is requested by setting CDFT = TRUE in the $rem section, as as by specifying a $cdft input section as described above. Additional job control variables are described below.

CDFT
       Initiates a constrained DFT calculation
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       TRUE Perform a Constrained DFT Calculation FALSE No Density Constraint
RECOMMENDATION:
       Set to TRUE if a Constrained DFT calculation is desired.

CDFT_POSTDIIS
       Controls whether the constraint is enforced after DIIS extrapolation.
TYPE:
       LOGICAL
DEFAULT:
       TRUE
OPTIONS:
       TRUE Enforce constraint after DIIS FALSE Do not enforce constraint after DIIS
RECOMMENDATION:
       Use the default unless convergence problems arise, in which case it may be beneficial to experiment with setting CDFT_POSTDIIS to FALSE. With this option set to TRUE, energies should be variational after the first iteration.

CDFT_PREDIIS
       Controls whether the constraint is enforced before DIIS extrapolation.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       TRUE Enforce constraint before DIIS FALSE Do not enforce constraint before DIIS
RECOMMENDATION:
       Use the default unless convergence problems arise, in which case it may be beneficial to experiment with setting CDFT_PREDIIS to TRUE. Note that it is possible to enforce the constraint both before and after DIIS by setting both CDFT_PREDIIS and CDFT_POSTDIIS to TRUE.

CDFT_THRESH
       Threshold that determines how tightly the constraint must be satisfied.
TYPE:
       INTEGER
DEFAULT:
       5
OPTIONS:
       N Constraint is satisfied to within 10-N.
RECOMMENDATION:
       Default value is set to match SCF_CONVERGENCE. Use the default unless problems occur.

CDFT_MAXITER
       Maximum number of iterations for converging the constraint.
TYPE:
       INTEGER
DEFAULT:
       20
OPTIONS:
       N A maximum of N microiterations will be attempted.
RECOMMENDATION:
       Default value is expected to be sufficient in most situations.

CDFT_PRINT
       Whether detailed information about CDFT iterations should be printed in the output file.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       TRUE Print detailed information. FALSE Do not print detailed information.
RECOMMENDATION:
       Use the default and invoke additional printing for troubleshooting.

CDFT_BECKE_POP
       Whether the calculation should print the Becke atomic charges at convergence
TYPE:
       LOGICAL
DEFAULT:
       TRUE
OPTIONS:
       TRUE Print Populations FALSE Do not print them
RECOMMENDATION:
       Use the default. Note that the Mulliken populations printed at the end of an SCF run will not typically add up to the prescribed constraint value. Only the Becke populations are guaranteed to satisfy the user-specified constraints.