Sharif Digital Repository

In this study, electronic structure, stability, and tendency to exchange electron of neutral, anionic, and cationic RhxCu4-x (x = 0-4) small clusters were investigated by density functional theory calculations. For neutral small clusters, it was found that the most stable structures of Rh4, Rh3Cu and Rh2Cu2 have distorted tetrahedral shape while the most stable structures of RhCu3 and Cu4 have quasi-planer shape. Adding charges to the clusters, caused shapes of the most stable structures undergo variations. Stabilities of the neutral, anionic, and cationic clusters decrease linearly with increasing the copper content. In addition, calculated chemical harnesses indicated that the small... 

Adsorption and dissociation of NO on RhxCu4-x(x = 0–4) nano clusters were investigated using density functional theory. Adsorption energy, total charge on NO, NO bond length, and NO vibrational frequency for various modes of NO adsorption were analyzed. Adsorption from the nitrogen end of NO on the Rh atom(s) of the clusters are more favored and adsorption energies are in the −1.02 eV to −2.59 eV range. NO binds stronger to Rh-Cu mixed clusters compared to pure Cu4 cluster, so N[sbnd]O bond is significantly weakened upon adsorption on the former. NO binding to more atoms of the clusters results in a corresponding decrease of the N[sbnd]O vibrational frequency. Dissociation of NO was also... 

Adsorption of molecular and atomic oxygen on neutral and negatively charged PdxCu3-x (x=0-3) nano-clusters have been studied by density functional theory. It has been observed that modes and energies of adsorption strongly depend on the charge and composition of the nano-clusters. The most stable adsorption mode for molecular oxygen on neutral Pd/Cu nano-clusters is to bridge Pd-Cu site (adsorption energy=-103.7kJmol-1) while on negatively charged nano-clusters bridging of Pd-Pd or Cu-Cu are more stable adsorption modes (adsorption energies=-140.9 and -172.9kJmol-1). Also, the most stable adsorption mode for atomic oxygen on neutral Pd/Cu nano-clusters is on the hollow site (adsorption... 

The potential energy function of sulphur hexafluoride has been determined via the inversion of reduced viscosity collision integrals at zero pressure and fitted to obtain an analytical potential form. A comparison of the potential with the previously determined potential has been included. The interaction potential energy from the inversion procedure reproduces, within experimental error, viscosity, self-diffusion coefficient, thermal conductivity and isotopic thermal diffusion factor of sulphur hexafluoride over a wide temperature range. These properties have also been fitted to very accurate equations  

A new pair-potential energy function of nitrogen has been determined via the inversion of reduced viscosity collision integrals and fitted to obtain an analytical potential form. The pair-potential reproduces the second virial coefficient, viscosity, thermal conductivity, self-diffusion coefficient, and thermal diffusion factor of nitrogen in a good accordance with experimental data over wide ranges of temperatures and densities. We have also performed the molecular dynamics simulation to obtain pressure, internal energy, heat capacity at constant volume, and self-diffusion coefficient of nitrogen at different temperatures and densities using our calculated pair-potential and some other...