Several FDET-based methods are available in the FDE-Man module of Q-Chem. The FDE-Man job control is accomplished in two sections, $rem and $fde.
The fragments are specified via the fragment descriptors (see Section 12) in the $molecule section, whereas the first fragment corresponds to the embedded species (A), the second fragment represents the environment (B).
Note: The current implementation allows only for closed shell fragments.
FDE
FDE
Turns density embedding on.
TYPE:
BOOLEAN
DEFAULT:
False
OPTIONS:
True
Perform an FDET calculation.
False
Don’t perform FDET calculation.
RECOMMENDATION:
Set the $rem variable FDE to TRUE to start a FDET calculation.
Enabling FDE-Man, the specification of the embedding method and other job control parameters (thresholds, max. iterations etc.) should be set in the $rem section.
METHOD
METHOD
Determines which FDET-based method should be used for the embedded wavefunction if FDE = TRUE.
TYPE:
STRING
DEFAULT:
None
OPTIONS:
NAME
Use METHOD = NAME, where NAME is either HF for Hartree-Fock theory or
else one of the DFT methods listed in Section 5.3.5.
RECOMMENDATION:
None
Other DFT functionals can also be requested with the EXCHANGE and CORRELATION keywords as described in Section 5.4.
Note: The current implementation is restricted to mean-field methods that are solved with the SCFMAN module.
The standard capabilities to use customized basis sets are also possible with the FDE-Man module.
FDE-ADC
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Link
is a density embedding method based on the
combination of the Algebraic Diagrammatic Construction scheme for the
polarization propagator (ADC, Section 7.11) and Frozen-Density
Embedding Theory (FDET).
In this particular variant, the subsystem A is represented by a wave function
whereas subsystem B is described by a density. The FDE-ADC method uses the
linearized FDET approximation.
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Similar to the other methods, the ADC specifications have to be done inside the $rem section, as shown below.
METHOD
METHOD
Determines which FDET-based method should be used if FDE = TRUE.
TYPE:
STRING
DEFAULT:
None
OPTIONS:
adc(2)
Perform an FDE-ADC(2)-s calculation.
adc(2)-x
Perform an FDE-ADC(2)-x calculation.
adc(3)
Perform an FDE-ADC(3) calculation (potential constructed with MP(2) density).
cvs-adc(2)
Perform an FDE-ADC(2)-s calculation of core excitations.
cvs-adc(2)-x
Perform an FDE-ADC(2)-x calculation of core excitations.
cvs-adc(3)
Perform an FDE-ADC(3) calculation of core excitations.
RECOMMENDATION:
None
FDE-ADC also supports the excited state analysis (STATE_ANALYSIS) carried out by the libwfa module.