11.7 Frozen-Density Embedding Theory

11.7.3 Single-fragment Calculations

(May 16, 2021)

FDE-Man allows the user to perform the embedding calculation by importing the embedding potential in its atomic-orbital matrix representation. Consequently, all the specifications needed to construct the embedding potential are no longer required. Additionally, the single-fragment mode is turned on when only one molecule is given in the MOLECULE section.

import_vmat
       Import the embedding potential in AO matrix representation. The expected file name is FDE_vembmat.txt and does not have a header. All the keywords related to fragment B and the embedding potential will cause an error.
INPUT SECTION: $fde
TYPE:
       BOOLEAN
DEFAULT:
       FALSE
OPTIONS:
       TRUE Read and add the embedding potential to the Fock matrix. FALSE Don’t read the embedding potential, use other options.
RECOMMENDATION:
       None

Note:  This functionality is constructed as a separate module, only the import_rhoA and print_props=1 options can be used with the single-fragment mode.

One can also use the single-fragment mode to obtain Mulliken and ChElPG charges from a density matrix. In order to do that, one needs to import the density of fragment A, and set charges to one of the options below. Importing the density matrix of fragment A is done as described previously.

charges
       Compute Mulliken or ChElPG charges from a density matrix in AO matrix representation. The import_rhoA option must be set to TRUE.
INPUT SECTION: $fde
TYPE:
       STRING
DEFAULT:
       None
OPTIONS:
       Mulliken Compute Mulliken charges from system A density matrix. CHELPG Compute ChElPG charges from system A density matrix.
RECOMMENDATION:
       None