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# 12.7.8 ALMO-EDA with Non-Perturbative Charge Transfer Analysis

(February 4, 2022)

Q-Chem also supports the non-perturbative 1155 (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 restricted SCF calculations only.

Set GEN_SCFMAN_EDA2 = 1 and EDA_VCT_A = 1 to use the non-perturbative CT analysis method (note: this feature is currently not compatible with jobs with EDA2 $>$ 0 and needs to be performed as a separate calculation) The result will print out the total energy and charge change in the charge transfer process, 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 accounts for more than $N$% of the energy or charge change between each fragment pair, whose default value is set to 5. Set EDA_PCT_A = 1 to do the perturbative CT analysis as well. To visualize the COVPs, set EDA_SAVE_COVP = 1 and GUI = 2. The saved COVPs will be written to an .fchk file, with the occupied orbitals called “Localized Alpha MO Coefficients (Boys)" and the corresponding virtual orbitals called “Localized Beta MO Coefficients (Boys)" (note: this is a workaround and visualization of COVPs in .fchk files will be enabled in future releases). One caveat is that the current implementation does not support the OCC_RI_K algorithm, and it will give wrong results if this REM 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_COVP_THRESH

EDA_COVP_THRESH
Specifies the significance above which the COVPs will be saved
TYPE:
INTEGER
DEFAULT:
5
OPTIONS:
$N$ COVPs that accounts for more than $N$% of the fragment-wise energy or charge transfer 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:
To save the COVPs as an fchk file, GUI = 2 also has to be set

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

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

$rem method = b3lyp sym_ignore = true symmetry = false basis = 6-31g* scf_algorithm = diis thresh = 12 incfock = 0 mem_total = 16000 scf_convergence = 9 child_mp = 1 child_mp_orders = 232 ! nDQ gen_scfman_eda2 = 1 eda_pct_a = 1 eda_vct_a = 1 eda_covp_thresh = 5 eda_save_covp = 1 gui = 2$end


View output