12.7 Second-Generation ALMO-EDA Method 12.7.7 ALMO-EDA with non-aufbau Electronic Configurations 12.7.9 Visualization Tools Associated with ALMO-EDA

12.7.8 ALMO-EDA with Non-Perturbative Polarization and Charge Transfer Analysis

(July 14, 2022)

Q-Chem also supports the non-perturbative ¹²²² Veccham S. P. et al.
Phys. Chem. Chem. Phys.
(2021), 23, pp. 928. Link (variational) energy and charge decomposition analysis in the second generation ALMO-EDA framework. The advantage of this method over the perturbative CT analysis method is that the energy and charge decompositions are both exact and there are no higher-order terms left. Currently, this method is implemented for both restricted and unrestricted SCF calculations, and is able to analyze both the polarization and charge transfer processes of intermolecular interactions.

The non-perturbative charge transfer analysis is currently not compatible with jobs with EDA2 $>$ 0 (see Sec. 12.7.5), and needs to be invoked by REM variable GEN_SCFMAN_EDA2 = 1. Perturbative CT analysis can be invoked by setting EDA_PCT_A = 1, while non-perturbative CT analysis by setting EDA_VCT_A = 1. The default analysis is performed for the charge transfer process, and setting EDA_POL_A = 1 will turn on the analysis for the polarization process as well. In the results, the changes in the total energy and charge will be printed out, as well as the pairwise energy and charge changes between fragments, with fragment labels starting from 0. Set EDA_COVP_THRESH = $N$ to print out COVPs that contribute more than $0.001\times N$ kJ/mol of energy lowering, and the default value is set to 500. To visualize the COVPs, set EDA_SAVE_COVP = 1, MAKE_CUBE_FILES = True and PLOTS = True. The saved COVPs will be written to a folder as cube files, which can be visualized using IQmol. UHF analysis will be automatically used if the system contains at least one open-shell fragment, and it can also be forced by setting UHF = 1. One caveat is that the current implementation does not support the OCC_RI_K algorithm, and the calculation will crash if this $rem varaiable is set true.

GEN_SCFMAN_EDA2

GEN_SCFMAN_EDA2
       Perform ALMO-EDA calculations using the GEN_SCFMAN_EDA2 driver (differing from jobs with EDA2 $>$ 0)
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Do not use the new ALMO-EDA framework 1 Use the new ALMO-EDA framework
RECOMMENDATION:
       Set to 1 to perform non-perturbative CT analysis

EDA_PCT_A

EDA_PCT_A
       Perform perturbative CT analysis
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Do not perform perturbative CT analysis 1 Perform perturbative CT analysis
RECOMMENDATION:
       Set to 1 to perform perturbative CT analysis

EDA_VCT_A

EDA_VCT_A
       Perform non-perturbative CT analysis
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Do not perform non-perturbative CT analysis 1 Perform non-perturbative CT analysis.
RECOMMENDATION:
       Set to 1 to perform non-perturbative CT analysis

EDA_POL_A

EDA_POL_A
       Perform EDA for polarization process
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Do not perform EDA for polarization process 1 Perform EDA for polarization process
RECOMMENDATION:
       Set to 1 to perform EDA for polarization process

EDA_COVP_THRESH

EDA_COVP_THRESH
       Specifies the significance above which the COVPs will be saved
TYPE:
       INTEGER
DEFAULT:
       500
OPTIONS:
       $N$ COVPs that contributes more than $0.001\times N$ kJ/mol in energy decrease will be saved
RECOMMENDATION:
       None

EDA_SAVE_COVP

EDA_SAVE_COVP
       Save significant COVPs or not
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Do not save significant COVPs 1 Save significant COVPs
RECOMMENDATION:
       Set to 1 to save COVPs. Note REMs for plotting cube files need also be set

Example 12.20 ALMO-EDA calculation for the H ${}_{2}$ O-Na ${}^{+}$ system with both perturbative and non-perturbative analysis for the polarization and charge transfer processes.

$molecule
1 1
--
0 1
H         -0.73946        0.94887        0.78379
O         -1.16910        0.63297       -0.02844
H         -2.12156        0.70793        0.14730
--
1 1
Na        -0.17266       -0.04338       -1.86190
$end

$rem
Method              B3LYP
scf_print_frgm         1
sym_ignore              = 1
SYMMETRY                false
basis                6-31G*
scf_algorithm               diis
thresh              = 12
incfock             = 0
mem_total               = 16000
scf_convergence             = 7
child_mp                1
child_mp_orders             232 ! nDQ
gen_scfman_eda2      1
eda_pol_a¯¯     1
eda_pct_a            1
eda_vct_a            1
eda_covp_thresh      500
eda_save_covp        1
make_cube_files      true
plots                true
$end

$plots
 grid_points 100 100 100
$end

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12.7.8 ALMO-EDA with Non-Perturbative Polarization and Charge Transfer Analysis