Use the auxiliary-density-matrix method (ADMM) for approximating the computation of the exchange Fock matrix and energy.

For detailed algorithms, see See Guidon, Hutter, and VandeVondele, J. Chem. Theory Comput. 6, 2348 (2010). .

It can be used inside dft() to speedup HF exchange calculations

dft(
structure(molecule=water)
xc = PBE0
ao = DZP
)

This command can appear in the global context.

### Options

auxiliary_ao

Name of the auxiliary AO basis set used in the ADMM approximation. This basis is used to project the density matrix from the primary AO basis to the smaller auxiliary AO basis, for approximating the computation of the exact exchange Fock matrix and energy.

No constraint is implied by the parser, but the basis set file must exist (in the directory basis within the data directory).

• The type is string-lowered
• The default is 3-21G
exchange_functional

Name of exchange functional to use for the ADMM approximations.

• The type is string-lowered
• The default is pbex
• The value must be one of:
• B88
• PBEX
• PBERX
radial_threshold

Threshold for radial density cutoff, used in screening in the evaluation of exchange-correlation functionals.

• The type is real
• The default is 1e-6
type

Specify the type of the ADMM approximation.

• The type is string
• The default is admm2
• The value must be one of: