Local density functional (LDF) theory has been used to calculate the geometry and vibrational frequencies of a set of transition-metal compounds in their molecular forms containing halogens, oxygens, alkyl groups, carbonyls, nitrosyls, and other substituents. The calculations were done with polarized double-zeta numerical and Gaussian basis sets, and the geometries were obtained by analytic gradient methods. The frequencies were evaluated by numerical differentiation of the analytic first derivatives. The results obtained with the numerical and the Gaussian basis sets were found to be in good agreement. The agreement with experiment for the geometries is quite good with an average mean deviation of 0.026 Á. The largest errors involve dative bonds with the LDF method predicting the bonds to be too short. Nonlocal corrections were applied to some of the methyl-carbonyl and metal-nitrosyl bond lengths, and this correction was found to lengthen the bonds to give better agreement with experiment. The frequencies are also predicted quite accurately. The LDF results are in much better agreement with experiment as compared to Hartree-Fock results.
The ionic dissociation of HF, HCl, and H2S in water is examined using density functional theory (DFT), Hartree–Fock (HF), and Mo/ller–Plesset theory to second order (MP2). The calculations show that HF, HCl, and H2S form fully dissociated stable clusters with four water molecules. Each cluster appears to be stabilized by the formation of six hydrogen bonds. These calculations also indicate that a minimum of four water molecules are required to form stable structures in which positive and negative ions coexist in the cluster. The hydrogen transfer between the acid and water molecules is very similar to the mechanism proposed for hydrogen transfer in water solutions. The binding energies of the hydrated hydrofluoric acid, hydrated hydrochloric acid, and hydrated hydrogen disulfide estimated with B-LYP are 37.51, 41.17, and 20.68 kcal/mol, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.