13.7 The Second-Generation ALMO-EDA Method

13.7.4 Job Control for EDA2

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
      (default: TRUE).

    • 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 POL:

    • CHILD_MP_ORDERS: as introduced in Section 13.7.2 (default: 232 (DQ)).

    • SCFMI_FREEZE_SS: as introduced in Section 13.7.1 (default: 0).

  • 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
      (default: FALSE).

    • 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.

EDA2
       Switch on EDA2 and specify the option set number.
TYPE:
       INTEGER
DEFAULT:
       2
OPTIONS:
       0 Do not run through EDA2. 1 Frozen energy decomposition + nDQ-FERF polarization (the standard EDA2 option) 2 Frozen energy decomposition + (AO-block-based) ALMO polarization (old scheme with the addition of frozen decomposition) 3 Frozen energy decomposition + oDQ-FERF polarization (NOT commonly used) 4 Frozen wave function relaxation + Frozen energy decomposition + nDQ-FERF polarization (NOT commonly used) 5 Frozen energy decomposition + polMO polarization (NOT commonly used). 10 No preset. Completely controlled by user’s $rem input (for developers only)
RECOMMENDATION:
       Turn on EDA2 for Q-Chem’s ALMO-EDA jobs unless CTA with the old scheme is desired. Option 1 is recommended in general, especially when substantially large basis sets are employed. The original ALMO scheme (option 2) can be used when the employed basis set is of small or medium size (arguably no larger than augmented triple-ζ). The other options are rarely used for routine applications.

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.

Example 13.14  Energy decomposition analysis for the ammonia-borane complex. The FERF-nDQ model is used for the POL term (as very large basis set is employed here), and decomposition of the frozen interaction energy is performed (Hartree-Fock is employed as the DFXC functional by default).

$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

Example 13.15  Energy decomposition analysis of the water dimer with a low-cost model chemistry. The original ALMO model is used for the evaluation of polarization energy, and revPBE is chosen as the DFXC functional. Counterpoise correction for the BSSE is applied.

$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, Esol, 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.

Example 13.16  EDA calculation for the water-Mg2+ complex in PCM water

$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