Parametrization of the PM7 Semiempirical Quantum Mechanical Method for Silver Nanoclusters

Semiempirical quantum mechanical
methods (SEQMs) are widely used
in computational chemistry because of their low computational cost,
but their accuracy depends on the quality of the parameters. The neglect
of diatomic differential overlap method PM7 is among the few SEQMs
that contain parameters for Ag, but the experimental reference data
was insufficient to obtain reliable parameters in the original parametrization.
In this work, we reparametrize the PM7 parameters for Ag to accurately
reproduce the ground-state potential energy surfaces of Ag clusters.
Since little experimental data is available, we use reference data
obtained from the ab initio method CCSD­(T). The resulting parameters
significantly reduce the errors in binding energies, energies required
to displace clusters along their normal modes, and relative energies
of isomers compared to the default PM7 Ag parameters.