The use of the FERF model for the evaluation of polarization energy and the further decomposition of the frozen term define the second generation of the ALMO-EDA method. Meanwhile, under the same code structure, the original AO-block based ALMO model and other related methods (such as the constrained relaxation of the frozen wave function391 which renders the frozen energy variationally computed, and the polMO model41 that arguably gives a lower limit to the polarization contribution) are also available. This entire set of methods implemented in Q-Chem based on GEN_SCFMAN (see Section 4.3) is referred to as “EDA2". In Q-Chem 5.2 and after, “EDA2" is used as the default ALMO-EDA driver when “JOBTYPE = EDA" is requested.
The job control for EDA2 is largely simplified by a series of preset options provided by the developers. The option number is set through the EDA2 $rem variable (introduced below). Besides that, for the sake of flexibility, users are allowed to overwrite the values of part of the preset $rem variables:
Related to the isolated fragment calculations:
EDA_CHILD_SUPER_BASIS: use the super-system basis for fragment calculations (default: FALSE).
FRAGMO_GUESS_MODE: as introduced in Section 13.3 (default: 0).
Related to the decomposition of the FRZ term:
FRZ_ORTHO_DECOMP: it can be turned off by setting its value to -1 in the $rem section
FRZ_ORTHO_DECOMP_CONV: as introduced in Section 13.7.3 (default: 6).
EDA_CLS_DISP: as introduced in Section 13.7.3 (default: FALSE).
DISP_FREE_X: as introduced in Section 13.7.3 (default: HF).
DISP_FREE_C: as introduced in Section 13.7.3 (default: NONE).
Related to the evaluation of CT and BSSE:
EDA_NO_CT: skip the evaluation of the CT term in the EDA procedure
(default: FALSE (automatically turned on when SCFMI_FREEZE_SS = TRUE)).
EDA_BSSE: use counterpoise-corrected monomer calculations to evaluate the BSSE
EDA_PCT_A: turn on perturbative charge transfer analysis (Roothaan step based).
EDA_COVP: perform COVP analysis for charge transfer (see Section 13.5).
EDA_PRINT_COVP: dump COVPs to the MO coefficient file (see Section 13.5). Note: EDA2 can automatically generate the cubes for the dominant complementary occupied-virtual orbitals for each pair of donor and acceptor fragments when EDA_PRINT_COVP is greater than 1.
Note that for Q-Chem 5.2 and after, if “JOBTYPE = EDA" is requested while the EDA2 $rem variable is not specified by the user, it automatically sets EDA2 = 2 and EDA_PCT_A = TRUE as the default option.
$molecule 0 1 -- 0 1 N 0.000000 0.000000 -0.727325 H 0.947371 0.000000 -1.091577 H -0.473685 -0.820448 -1.091577 H -0.473685 0.820448 -1.091577 -- 0 1 B 0.000000 0.000000 0.930725 H -1.165774 0.000000 1.243063 H 0.582887 -1.009590 1.243063 H 0.582887 1.009590 1.243063 $end $rem JOBTYPE eda EDA2 1 METHOD wB97M-V BASIS def2-TZVPPD SYMMETRY false MEM_TOTAL 4000 MEM_STATIC 1000 THRESH 14 SCF_CONVERGENCE 8 XC_GRID 000099000590 NL_GRID 1 FD_MAT_VEC_PROD false $end
$molecule 0 1 -- 0 1 H1 O1 H1 0.95641 H2 O1 0.96500 H1 104.77306 -- 0 1 O2 H2 dist O1 171.85474 H1 180.000 H3 O2 0.95822 H2 111.79807 O1 -58.587 H4 O2 0.95822 H2 111.79807 O1 58.587 dist = 2.0 $end $rem JOBTYPE eda EDA2 2 METHOD b97m-v BASIS def2-svpd SCF_CONVERGENCE 8 THRESH 14 SYMMETRY false DISP_FREE_X revPBE DISP_FREE_C PBE EDA_BSSE true $end
In real applications, it is often desirable to perform EDA under a solvent environment. Q-Chem 5.2 added the support for PCM and SMD models in EDA2. The setup of solvent models in the input is the same as in standard SCF calculations with PCM/SMD. For these EDA jobs, the interaction energy to be decomposed is defined as the energy difference between separately solvated monomers (non-interacting) and the solvated complex. A new term, , is introduced to describe the change in solvation energy upon the formation of frozen complex. Besides that, the other terms are defined in the same way as in gas-phase ALMO-EDA while they are calculated in the presence of solvent model.
$molecule 2 1 -- 0 1 H1 H2 H1 1.55618 O1 H2 0.97619 H1 37.14891 -- 2 1 Mg1 O1 scan H2 127.14892 H1 180.0 scan = 1.91035 $end $rem jobtype eda eda2 2 method wb97m-v basis 6-31+g(d) unrestricted false scf_algorithm diis scf_convergence 8 max_scf_cycles 200 thresh 14 symmetry false sym_ignore true solvent_method pcm eda_cls_disp true $end $PCM THEORY CPCM METHOD SWIG SOLVER INVERSION HPOINTS 302 HEAVYPOINTS 302 $END $SOLVENT DIELECTRIC 78.39 $END