Validation of density functionals, semiempirical methods, and new multicoefficient correlation methods for Zn coordination chemistry

Zinc compounds have important commercial applications in the petroleum industry as additives and as hydrogen sulfide scrubbing agents in the refining process. Zinc also finds broad manufacturing uses and is present in biologically important macromolecules. Molecular modeling of zinc centers in molecules of all sizes, from small diatomics to macromolecules, nanoparticles and ores, is limited by the lack of reliable Zn parameters and is complicated by unusual coordination at transition states. Here we present parameter databases of bond distances and angles together with dipole moments for a selection of representative zinc model compounds using a wide variety of density-functional theory levels, semiempirical methods, self-consistent-charge density-functional tight-binding theory, coupled-cluster theory, and two new multicoeffient correlation methods (MCCM) derived especially for zinc centers. The best density functionals for treating zinc centers are specified, and new parameters are obtained that together with optimized functional forms and the aforementioned MCCM methods, can prove useful for analyzing Zn centers in diverse research settings.