A simulation protocol based on fragment molecular orbital−based molecular dynamics (FMO-MD) was applied to a droplet model consisting of a divalent copper ion and 64 water molecules. The total energy and forces were evaluated at the unrestricted Hartree-Fock (UHF) level with three-body fragment correction (FMO3). Two MD runs were performed: one with a six-coordination setting and the other with a five-coordination setting in the first hydration shell. Both runs resulted in the main peak position of the Cu-O radial distribution function at 2.02 Å, in reasonable agreement with the experimental data. The O-Cu-O angular distribution function showed different characteristics between the two cases.
We have developed a couple of optimal damping algorithms (ODAs) for unrestricted Hartree-Fock (UHF) calculations of open-shell molecular systems. A series of equations were derived for both concurrent and alternate constructions of α and β Fock matrices in the integral-direct self-consistent-field (SCF) procedure. Several test calculations were performed to check the convergence behaviors. It was shown that the concurrent algorithm provides better performance than does the alternate one.