Pd. Lyne et al., A hybrid QM-MM potential employing Hartree-Fock or density functional methods in the quantum region, J PHYS CH A, 103(18), 1999, pp. 3462-3471
A hybrid quantum mechanical-molecular mechanical (QM-MM) potential energy f
unction with ab initio and density functional capabilities has been impleme
nted in the CHARMM program. It makes use of the quantum mechanical program
CADPAC and the CHARMM molecular mechanics energy function; a GAMESS(US) int
erface to the CHARMM program was already available. To test the methodology
, a series of relatively small systems are studied and comparisons are made
of full QM calculations with those from various QM-MM partitions. Both den
sity functional and Hartree-Fock calculations for the quantum region are pr
esented aid, where possible, compared with results from previous AM1-MM cal
culations. For the density functional based QM-MM calculations, the LDA and
BLYP functionals were used. The performances of both the density functiona
l and Hartree-Fock based QM-MM calculations compare well with pure quantum
calculations. The link atom method was tested by performing a number of QM-
MM simulations on the complexes of metal cations with model ligands of biol
ogical interest. It was found that it gave good results for the structures,
binding energies, and charge distributions.