$MOROKM

$MOROKM group (relevant for RUNTYP=MOROKUMA)

This group controls how the supermolecule input in the $DATA group is divided into two or more monomers. Both the supermolecule and its constituent monomers must be well described by RHF wavefunctions.

MOROKM
= a flag to request Morokuma-Kitaura decomposition. (default is .TRUE.)

RVS
= a flag to request "reduced variation space" decomposition. This differs from the Morokuma option, and one or the other or both may be requested in the same run. (default is .FALSE.)

BSSE
= a flag to request basis set superposition error be computed. You must ensure that CTPSPL is selected. This option applies only to MOROKM decompositions, as a basis superposition error is automatically generated by the RVS scheme. This is not the full Boys counterpoise correction, as explained in the reference. (default is .FALSE.)


IATM
= An array giving the number of atoms in each of the monomer. Up to ten monomers may be defined. Your input in $DATA must have all the atoms in the first monomer defined before the atoms in the second monomer, before the third monomer... The number of atoms belonging to the final monomer can be omitted. There is no sensible default for IATM, so don't omit it from your input.

ICHM
= An array giving the charges of the each monomer. The charge of the final monomer may be omitted, as it is fixed by ICH in $CONTRL, which is the total charge of the supermolecule. The default is neutral monomers, ICHM(1)=0,0,0,...

EQUM
= a flag to indicate all monomers are equivalent by symmetry (in addition to containing identical atoms). If so, which is not often true, then only the unique computations will be done. (default is .FALSE.)

CTPSPL
= a flag to decompose the interaction energy into charge transfer plus polarization terms. This is most appropriate for weakly interacting monomers. (default is .TRUE.)

CTPLX
= a flag to combine the CT and POL terms into a single term. If you select this, you might want to turn CTPSPL off to avoid the extra work that that decomposition entails, or you can analyze both ways in the same run (default=.FALSE.)

RDENG
= a flag to enable restarting, by reading the lines containing "FINAL ENERGY" from a previous run. These should be edited from an incomplete log file and placed in a $ENERGY group. (default is .FALSE.)


References: C.Coulson in "Hydrogen Bonding", D.Hadzi, H.W.Thompson, Eds., Pergamon Press, NY, 1957, pp 339-360.
C.Coulson Research, 10, 149-159 (1957).
K.Morokuma J.Chem.Phys. 55, 1236-44 (1971).
K.Kitaura, K.Morokuma Int.J.Quantum Chem. 10, 325 (1976).
K.Morokuma, K.Kitaura in "Chemical Applications of Electrostatic Potentials", P.Politzer,D.G.Truhlar, Eds. Plenum Press, NY, 1981, pp 215-242.

The method coded is the newer version described in the latter two papers. Note that the CT term is computed separately for each monomer, as described in the words below equation 16 of the 1981 paper, not simultaneously.

Reduced Variational Space:
W.J.Stevens, W.H.Fink, Chem.Phys.Lett. 139, 15-22(1987).

BSSE during Morokuma decomposition:
R.Cammi, R.Bonaccorsi, J.Tomasi Theoret.Chim.Acta 68, 271-283(1985).

The present implementation:
"Energy decomposition analysis for many-body interactions, and application to water complexes" W.Chen, M.S.Gordon J.Phys.Chem. 100, 14316-14328(1996)

The present implementation has some quirks:

  1. The initial guess of the monomer orbitals is not controlled by $GUESS. The program first looks for a $VEC1, $VEC2, ... group for each monomer. If they are found, they will be MOREAD. If any of these are missing, the guess for that monomer will be constructed by HCORE. Check your monomer energies carefully!
  2. The use of symmetry is turned off internally.
  3. There is no direct SCF option. File ORDINT will contain a full C1 list of integrals. File AOINTS will contain whatever subset of these is needed for each particular decomposition step. So extra disk space is needed compared to RUNTYP=ENERGY.
  4. The option applies only to ab initio cases, and it will run in parallel.

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