# 5.5.5 Incremental DFT

(June 30, 2021)

Incremental DFT (IncDFT) uses the difference density and functional values to improve the performance of the DFT quadrature procedure by providing a better screening of negligible values. Using this option will yield improved efficiency at each successive iteration due to more effective screening.

INCDFT
Toggles the use of the IncDFT procedure for DFT energy calculations.
TYPE:
LOGICAL
DEFAULT:
TRUE
OPTIONS:
FALSE Do not use IncDFT TRUE Use IncDFT
RECOMMENDATION:
Turning this option on can lead to faster SCF calculations, particularly towards the end of the SCF. Please note that for some systems use of this option may lead to convergence problems.

INCDFT_DENDIFF_THRESH
Sets the threshold for screening density matrix values in the IncDFT procedure.
TYPE:
INTEGER
DEFAULT:
SCF_CONVERGENCE + 3
OPTIONS:
$n$ Corresponding to a threshold of $10^{-n}$.
RECOMMENDATION:
If the default value causes convergence problems, set this value higher to tighten the threshold.

INCDFT_GRIDDIFF_THRESH
Sets the threshold for screening functional values in the IncDFT procedure
TYPE:
INTEGER
DEFAULT:
SCF_CONVERGENCE + 3
OPTIONS:
$n$ Corresponding to a threshold of $10^{-n}$.
RECOMMENDATION:
If the default value causes convergence problems, set this value higher to tighten the threshold.

INCDFT_DENDIFF_VARTHRESH
Sets the lower bound for the variable threshold for screening density matrix values in the IncDFT procedure. The threshold will begin at this value and then vary depending on the error in the current SCF iteration until the value specified by INCDFT_DENDIFF_THRESH is reached. This means this value must be set lower than INCDFT_DENDIFF_THRESH.
TYPE:
INTEGER
DEFAULT:
0 Variable threshold is not used.
OPTIONS:
$n$ Corresponding to a threshold of $10^{-n}$.
RECOMMENDATION:
If the default value causes convergence problems, set this value higher to tighten accuracy. If this fails, set to 0 and use a static threshold.

INCDFT_GRIDDIFF_VARTHRESH
Sets the lower bound for the variable threshold for screening the functional values in the IncDFT procedure. The threshold will begin at this value and then vary depending on the error in the current SCF iteration until the value specified by INCDFT_GRIDDIFF_THRESH is reached. This means that this value must be set lower than INCDFT_GRIDDIFF_THRESH.
TYPE:
INTEGER
DEFAULT:
0 Variable threshold is not used.
OPTIONS:
$n$ Corresponding to a threshold of $10^{-n}$.
RECOMMENDATION:
If the default value causes convergence problems, set this value higher to tighten accuracy. If this fails, set to 0 and use a static threshold.