To perform a GMBE(1) calculation, set GMBE_INT =
TRUE in the $rem section. The level of theory applied to the
fragments will correspond to the method specified in the $rem section. Researchers utilizing
Q-Chem’s GMBE implementation are requested to cite
Refs.
69
J. Chem. Phys.
(2023),
159,
pp. 074107.
Link
and
1120
J. Chem. Phys.
(2012),
137,
pp. 064113.
Link
.
The following keywords control the GMBE calculation in Q-Chem. They should be specified in the $rem section of the input file.
GMBE_INT
GMBE_INT
Perform a GMBE Calculation.
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
TRUE
Perform GMBE.
FALSE
Do not perform GMBE.
RECOMMENDATION:
NONE
GMBE_METHOD
GMBE_METHOD
Specify whether to perform an energy-based GMBE (GMBE-EB) or a density matrix-based GMBE (GMBE-DM).
TYPE:
INTEGER
DEFAULT:
1
OPTIONS:
1
Perform GMBE-EB.
2
Perform GMBE-DM.
RECOMMENDATION:
NONE
GMBE_ALGO
GMBE_ALGO
Specify the cutoff distance criterion used to determine the primitive fragments.
TYPE:
INTEGER
DEFAULT:
1
OPTIONS:
1
Minimum distance
2
Heavy-atoms distance
RECOMMENDATION:
NONE
GMBE_PRIMARY
GMBE_PRIMARY
Specify the primary cutoff distance used to determine the primitive fragments.
The input for GMBE_PRIMARY is the desired cutoff distance in Å, multiplied by 1000.
For example, to use a 2.00 Å cutoff distance, set GMBE_PRIMARY to 2000.
Similarly, if GMBE_PRIMARY = 3500, the cutoff distance will be 3.5 Å.
TYPE:
INTEGER
DEFAULT:
3000
OPTIONS:
The desired cutoff is = 1000, where is the cutoff distance in Å.
RECOMMENDATION:
NONE
GMBE_MAX_PRIM_CARD
GMBE_MAX_PRIM_CARD
Set the maximum cardinality for the primitive fragments.
TYPE:
INTEGER
DEFAULT:
5
OPTIONS:
represents the maximum cardinality of the primitive fragments.
RECOMMENDATION:
NONE
MBEDM_PURE
MBEDM_PURE
Perform McWeeny purification
901
Rev. Mod. Phys.
(1960),
32,
pp. 335.
Link
for GMBE density matrix.
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
TRUE
Perform McWeeney purification on the GMBE density matrix.
FALSE
Do not perform McWeeney purification on the GMBE density matrix.
RECOMMENDATION:
NONE
GMBE_DM_GUESS_ONLY
GMBE_DM_GUESS_ONLY
Evaluate the total energy of the system directly using GMBE-DM density matrix.
Enabling this option skips SCF iterations, preventing further convergence to the supersystem result.
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
TRUE
Do not perform SCF iterations and directly evaluate the total energy of the system using the GMBE-DM density matrix.
FALSE
Perform SCF iterations with the GMBE-DM density matrix as the initial guess.
RECOMMENDATION:
NONE
GMBE_PRINT_LEVEL
GMBE_PRINT_LEVEL
Control the level of details printed in the output file
TYPE:
INTEGER
DEFAULT:
1
OPTIONS:
1
Minimal output
2
Detailed output
RECOMMENDATION:
NONE
Example 12.47 Example of a GMBE(1)-EB calculation for a water hexamer.
$rem GEN_SCFMAN FALSE SYM_IGNORE TRUE METHOD B3LYP BASIS def2-TZVPPD THRESH 14 SCF_CONVERGENCE 7 MAX_SCF_CYCLES 200 MEM_TOTAL 8000 MEM_STATIC 4000 AO2MO_DISK 5000 GMBE_INT TRUE ! Perform GMBE GMBE_METHOD 1 ! 1 = energy-based, 2 = density matrix-based GMBE_ALGO 1 GMBE_PRIMARY 2000 GMBE_MAX_PRIM_CARD 5 GMBE_PRINT_LEVEL 1 !1 = minimal output, 2 = detailed output $end $molecule 0 1 -- 0 1 O -1.126149 -1.748387 -0.423240 H -0.234788 -1.493897 -0.661862 H -1.062789 -2.681331 -0.218819 -- 0 1 O -0.254210 1.611495 -1.293845 H -1.001520 1.163510 -1.690129 H -0.153399 2.411746 -1.809248 -- 0 1 O 1.694541 -0.226287 1.705739 H 0.785920 0.073487 1.677909 H 2.047134 0.150917 2.511706 -- 0 1 O -0.864533 0.522472 1.218817 H -0.694120 1.093542 0.469789 H -1.131418 -0.310426 0.829702 -- 0 1 O -2.312727 0.054310 -2.138177 H -2.002512 -0.686744 -1.617757 H -3.266931 0.004778 -2.081349 -- 0 1 O 1.292355 -0.704768 -0.977342 H 1.642300 -0.601085 -0.092386 H 0.948122 0.159656 -1.202018 $end
Example 12.48 Example of generating an initial guess density matrix using a GMBE(1)-DM calculation for a water hexamer.
$rem GEN_SCFMAN FALSE SYM_IGNORE TRUE METHOD B3LYP BASIS def2-TZVPPD THRESH 14 SCF_CONVERGENCE 7 MAX_SCF_CYCLES 200 MEM_TOTAL 4000 MEM_STATIC 4000 ao2mo_disk 5000 GMBE_INT TRUE ! Perform GMBE GMBE_METHOD 2 ! 1 = energy-based, 2 = density matrix-based GMBE_ALGO 1 GMBE_PRIMARY 2000 GMBE_MAX_PRIM_CARD 5 GMBE_DM_GUESS_ONLY FALSE ! Perform SCF iterations with the GMBE-DM initial guess GMBE_PRINT_LEVEL 1 ! 1 = minimal output, 2 = detailed output MBEDM_PURE TRUE ! Perform purification $end $molecule 0 1 -- 0 1 O -1.126149 -1.748387 -0.423240 H -0.234788 -1.493897 -0.661862 H -1.062789 -2.681331 -0.218819 -- 0 1 O -0.254210 1.611495 -1.293845 H -1.001520 1.163510 -1.690129 H -0.153399 2.411746 -1.809248 -- 0 1 O 1.694541 -0.226287 1.705739 H 0.785920 0.073487 1.677909 H 2.047134 0.150917 2.511706 -- 0 1 O -0.864533 0.522472 1.218817 H -0.694120 1.093542 0.469789 H -1.131418 -0.310426 0.829702 -- 0 1 O -2.312727 0.054310 -2.138177 H -2.002512 -0.686744 -1.617757 H -3.266931 0.004778 -2.081349 -- 0 1 O 1.292355 -0.704768 -0.977342 H 1.642300 -0.601085 -0.092386 H 0.948122 0.159656 -1.202018 $end