ACE

References: Lin2016

Parameters for the Adaptively Compressed Exchange (ACE) operator. ACE replaces the full exchange matrix with a low-rank projector K_ACE = -W*W^T after an initial full HFX build, reducing cost of subsequent SCF steps. NOTE: ACE requires diagonalization-based SCF. It is incompatible with orbital transformation (OT) methods because OT does not construct MO coefficients. [Edit on GitHub]

Keywords

• ACTIVE

• REBUILD_FREQUENCY

Keyword descriptions

ACTIVE: logical = F

Lone keyword: T

Usage: ACTIVE .TRUE.

Enable the ACE approximation for HFX. When .TRUE., the exchange matrix is replaced by the ACE projector after the first full build. [Edit on GitHub]

REBUILD_FREQUENCY: integer = 20

Usage: REBUILD_FREQUENCY 20

Rebuild the ACE projectors W every N SCF steps. N=1 means rebuild every step (identical to full HFX, use for testing only). N=10-20 is typical for production. Projectors are always rebuilt when the structure changes. [Edit on GitHub]