Q-Chem also supports the non-perturbative
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(2021),
23,
pp. 928.
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(variational) energy and
charge decomposition analysis in the second-generation ALMO-EDA framework through the eda2 driver. 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 eligible to analyze both
polarization
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J. Chem. Theory Comput.
(2023),
19,
pp. 8624.
Link
(POL) and charge transfer (CT) processes of intermolecular interactions.
The non-perturbative POL and CT analysis can be invoked by setting EDA_POL_A = TRUE and
EDA_VCT_A = TRUE, respectively. The POL analysis
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pp. 8624.
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uses the recently developed
fragment density matrix connecting method and can break the energy lowering and charge shift in the POL process into
exactly fragment-wise additive sums. The CT analysis will print out the pairwise energy and charge changes between fragments
as matrices, with fragment labels starting from 1, following the orders in the Q-Chem fragment input. The
interpretation is that the energy lowering and charge transfer happens due to electron donation from the fragments labeled
in the rows to the fragments labeled in the columns.
The default orbital analysis method is the complementary occupied-virtual pairs (COVP) method. To select the significant COVPs,
set EDA_COVP_THRESH = to print out the COVPs that contributes more than kJ/mol to the energy
decrease, and the default value is set to 500. To visualize the COVPs, set EDA_SAVE_COVP = TRUE,
MAKE_CUBE_FILES = TRUE and PLOTS = TRUE to save the orbitals as cube files, which can
be visualized using IQmol, VMD, or other visualization software. The natural orbitals for chemical valence (NOCV) analysis can also be
performed by setting EDA_NOCV = TRUE. To select the significant NOCVs, set EDA_NOCV_THRESH =
to print out NOCVs that contributes more than kJ/mol to energy decrease, and the default value is also set to 500.
The NOCV analysis includes the POL process, CT process, and the traditional NOCV results which combine the POL and CT processes.
As pointed out in this paper
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(2022),
18,
pp. 7428.
Link
, the ETS-NOCV method approximates the effective Fock matrix integration with only one quadrature,
which is set by EDA_NOCV_QUADRATURE =1, and Q-Chem also supports 5-quadratures for systems with significant density changes.
As an improvement upon the NOCVs, the recently proposed occupied-virtual orbitals for chemical valence (OVOCV)
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(2024),
128,
pp. 5202.
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can also be used
to analyse the CT step. The OVOCVs block-diagonalize the density difference operator into 2 2 blocks, which are spanned by one level
that is filled in the initial state (the occupied OVOCV) and one that is empty (the virtual OVOCV), making them much easier to interpret than
the NOCVs. For a more detailed introduction to OVOCV analysis, we refer the users to 10.3.4. To enable OVOCV analysis,
set OVOCV_ANALYSIS = 1 and OVOCV_THRESH = to print out the OVOCVs that contributes
more than kJ/mol to the energy decrease.
Unrestricted analysis will be used if at least one of the fragments has an open-shell structure. It can also be forced by setting UNRESTRICTED=TRUE.
EDA_POL_A
EDA_POL_A
Perform EDA for polarization process
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
FALSE
Do not perform EDA for polarization process
TRUE
Perform EDA for polarization process
RECOMMENDATION:
Set to TRUE to perform EDA for polarization process
EDA_VCT_A
EDA_VCT_A
Perform non-perturbative CT analysis
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
FALSE
Do not perform non-perturbative CT analysis
TRUE
Perform non-perturbative CT analysis.
RECOMMENDATION:
Set to TRUE to perform non-perturbative CT analysis
EDA_COVP_THRESH
EDA_COVP_THRESH
Specifies the significance above which the COVPs will be saved
TYPE:
INTEGER
DEFAULT:
500
OPTIONS:
COVPs that contributes more than kJ/mol in energy decrease will be saved
RECOMMENDATION:
None
EDA_SAVE_COVP
EDA_SAVE_COVP
Save significant COVPs or not
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
FALSE
Do not save significant COVPs
TRUE
Save significant COVPs
RECOMMENDATION:
Set to TRUE to save COVPs. Note that REMs for plotting cube files need also be set
EDA_NOCV
EDA_NOCV
Perform NOCV analysis
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
FALSE
Do not do NOCV analysis
TRUE
Do NOCV analysis
RECOMMENDATION:
None
EDA_NOCV_THRESH
EDA_NOCV_THRESH
Specifies the significance above which the NOCVs will be saved
TYPE:
INTEGER
DEFAULT:
500
OPTIONS:
NOCVs that contributes more than kJ/mol in energy decrease will be saved
RECOMMENDATION:
None
EDA_SAVE_NOCV
EDA_SAVE_NOCV
Save significant NOCVs or not
TYPE:
INTEGER
DEFAULT:
0
OPTIONS:
0
Do not save significant NOCVs
1
Save significant NOCVs
RECOMMENDATION:
Set to 1 to save NOCVs. Note REMs for plotting cube files need also be set
EDA_NOCV_QUADRATURE
EDA_NOCV_QUADRATURE
Number of quadratures used to integrate effective fock matrix
TYPE:
INTEGER
DEFAULT:
1
OPTIONS:
1
Use 1 quadrature
5
Use 5 quadratures
RECOMMENDATION:
Most of the time, one quadrature is enough. However, in cases where the NOCV energy decreases are very different from the corresponding COVP results, it is recommended to increase the quadrature numbers.
OVOCV_ANALYSIS
OVOCV_ANALYSIS
Perform OVOCV analysis
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
FALSE
Do not do OVOCV analysis
TRUE
Do OVOCV analysis
RECOMMENDATION:
None
OVOCV_THRESH
OVOCV_THRESH
Specifies the significance above which the OVOCVs will be saved
TYPE:
INTEGER
DEFAULT:
500
OPTIONS:
OVOCVs that contributes more than kJ/mol in energy decrease will be saved
RECOMMENDATION:
None
SAVE_OVOCV
SAVE_OVOCV
Save significant OVOCVs or not
TYPE:
INTEGER
DEFAULT:
0
OPTIONS:
0
Do not save significant OVOCVs
1
Save significant OVOCVs
RECOMMENDATION:
Set to 1 to save OVOCVs. Note REMs for plotting cube files need also be set
Example 12.20 Restricted EDA calculation for the HO-Na system with non-perturbative POL and CT analysis.
$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 $comment EDA2 (R) calculation with variational POL and CT analyses based on the eda2 driver $end $rem jobtype eda eda2 1 method B3LYP scf_print_frgm 1 basis 6-31G* scf_algorithm diis thresh 12 incfock false mem_total 16000 scf_convergence 7 scf_final_print 2 eda_pol_a 1 eda_vct_a 1 eda_covp_thresh 500 eda_save_covp 0 make_cube_files true plots true point_group_symmetry false integral_symmetry false $end $plots grid_points 50 50 50 $end
Example 12.21 Unrestricted EDA calculation for the CH-Na system with non-perturbative POL and CT analysis.
$molecule 1 2 -- 0 2 C¯-1.447596 -0.000023 0.000019 H¯-1.562749 0.330361 -1.023835 H¯-1.561982 0.721445 0.798205 H¯-1.561187 -1.052067 0.225866 -- 1 1 Na¯ 1.215591 0.000036 -0.000032 $end $comment EDA2 (U) calculation with variational POL and CT analyses based on the eda2 driver $end $rem jobtype eda eda2 1 method B3LYP scf_print_frgm true basis aug-cc-PVTZ scf_algorithm diis thresh 12 incfock false mem_total 16000 scf_convergence 7 eda_pol_a 1 eda_vct_a 1 eda_covp_thresh 500 eda_save_covp 0 make_cube_files true plots true point_group_symmetry false integral_symmetry false $end $plots grid_points 50 50 50 $end
Example 12.22 Unrestricted EDA calculation for the Rn-CH system with non-perturbative POL and CT analysis and NOCV analysis
$molecule 1 2 -- 0 1 C 0.0551597051 0.0364080371 -0.0375528310 H -0.0563410694 -1.0144740143 -0.3153331540 H -0.0537558345 0.7868509829 -0.8318467516 H -0.8718690962 0.2438110339 0.5677588397 H 1.0408273042 0.1810559688 0.4109829953 -- 1 2 Rn -0.2646060092 0.6373989916 3.0026329017 $end $rem jobtype eda eda2 1 method b3lyp scf_print_frgm 1 basis def2-tzvp ecp def2-ecp scf_algorithm diis thresh 12 incfock 0 mem_total 16000 scf_final_print 2 iprint 20000000 scf_convergence 7 eda_pol_a 1 eda_vct_a 1 eda_save_covp 0 eda_nocv 1 eda_save_nocv 0 eda_covp_thresh 500 eda_nocv_thresh 500 eda_nocv_quadrature 1 make_cube_files true plots true point_group_symmetry false integral_symmetry false $end $plots grid_points 100 100 100 $end
Example 12.23 Restricted EDA calculation for the ethene- system with non-perturbative POL and CT analysis. OVOCV analysis is enabled for CT analysis.
$molecule -1 1 -- 0 1 C -2.1241906261 0.4405879048 -0.6028769327 H -2.2759080470 0.1247332923 -1.6303256895 H -2.2970177347 1.4883974948 -0.3784045735 C -2.1383367135 -0.5060266611 0.4271962891 H -2.3004855320 -1.5544440597 0.1975704475 H -2.3216355550 -0.1916949240 1.4498166705 -- -1 1 Pt -0.1374350284 -0.0292366293 -0.0576671311 Cl -0.1541352882 -1.7330117528 -1.6304294395 Cl 2.1808813192 -0.0260821423 -0.0234510188 Cl -0.2063937942 1.6741234771 1.5139773781 $end $rem jobtype eda eda2 1 eda_bsse 0 method wb97x-v scf_print_frgm 1 sym_ignore 1 symmetry false basis def2-svp ecp def2-ecp scf_algorithm diis thresh 14 incfock 0 mem_total 16000 scf_final_print 2 scf_convergence 8 eda_pol_a 1 eda_vct_a 1 eda_covp_thresh 10000 eda_save_covp 0 eda_nocv 1 eda_save_nocv 0 eda_nocv_thresh 10000 eda_nocv_quadrature 5 ovocv_analysis 1 ovocv_thresh 10000 save_ovocv 0 make_cube_files true plots true $end $plots grid_points 50 50 50 $end