A Density Functional Theory Study Of The Interaction Of H₂with Os Clusters

Since5d transition metals such as Os, possess characteristics of high melting point and high bulk modulus and their compounds and alloys have super-hard materials and less attrition characteristics, they have been applied in fields such as super-hard materials, alloys, and so on.In this paper, Dmol3program based on First-principles density functional theory with generalized gradient approximation is applied. The geometric structures of Osn(n=11～16) clusters and (OsH2)n(n=1-5) clusters are all optimized systematically, and the ground state structures are investigated. The main results are as follows:Firstly, the possible equilibrium geometries of Osn(n=11-16) clusters are optimized by using the First-principles density functional theory at the generalized gradient approximation (GGA) level. For the ground state structures, the average binding energies, second-order difference of energy analysis, HOMO-LUMO gap are analyzed. The calculated results show that:The ground state structures show "odd-even" oscillation effect, the cluster is more stable when atomic number is even than odd, and with the increase of atoms number, the thermodynamics stability of clusters is better.Secondly, the ground state structures of Osn(n=11-16) clusters are analyzed carefully, after what we get already. In magnetic aspects, electronic spin density figures and density of state figures were used to show the main magnetic origin of Osn(n=11-16) clusters, Among the ground state structures, the magnetic moment of Os12clusters is quenched, there are ferromagnetic coupling and reversed ferromagnetic coupling in the rest clusters; we analyzed also the infrared vibration features and relevant vibration modes of Osn(n=11-16) clusters.Thirdly, after getting the ground state structures of (OsH2)n(n=1-5) clusters, the average binding energies, second-order difference of energy analysis, magnetic and the atomic charge are analyzed carefully. In magnetic aspects, the total magnetic moment of OsH2and (OsH2)2clusters are both2μB, the rest clusters are all OμB. The reason is the electron-pair effect between the H atom and the Os atom. If all the electrons between the H atom and the Os atom all make a pair, the magnetic moment of the clusterwill be quenched. When n<4, the electrons transter from Os atom to the H atom; if n=5, both the Os atom and the H atom have the ability to gain or lose electronic. When turn to Os atom, compared with gain electrons, it will lose more electrons.