Density Functional Theory Study For Osmium Clusters And Its Borides

The structures and some relative properties of Osn(n=17-22) clusters,OsnB(n=11-20) clusters and OsmBn(m+n≤5) clusters are computed using DensityFunctional Theory (DFT) in the DMOL3package. Results are as follows:(1) Using spin-polarized generalized gradient approximation (GGA) with PW91functional for calculating the structure and magnetic properties of Osn(n=17-22)clusters. And found that the most favorite geometries of Osnclusters with the sizes ofn=17-18turn into a cage that is somewhat compressed, most of these cages are basedon the close-packed hexagonal structure, and from Os19to Os22cluster theground-state seems to favor the globular cage. When n=18, Osnclusters mightpossess relatively high stabilities, which means the magic numbers structure is Os18.And in the electron spin density maps, the contribution to the total magnetic momentmainly come from the periphery atoms when n=17-18, and from Os19to Os22cluster,they mainly come from the cage structure. From the analysis of infraredspectroscopy, the highest peaks of Os18and Os20cluster have relatively highvibration intensity which is mostly concentrate upon100-200cm-1.(2) Using DFT-GGA study the geometries, stabilities, electronic and magneticproperties of OsnB (n=11-20) clusters. Os12B, Os15B, Os17B and Os19B clusters arefound to have relatively high stabilities and the B atom has little influence on OsnBcluster in total energy. Os14B cluster has the biggest magnetism among all theclusters, and the local magnetic moment of B atom does little effect to the totalmagnetic moment. The highest peaks of OsnB (n=11-17) clusters’ infraredspectroscopy are less than the cluster when n=18-20, this is because the structure haschanged when>18, the major functional group has become the globular cage.(3) OsmBn(m+n≤5) clusters was systematically studied by using DFT. Whenn=2-4, the neutral OsmBn(m+n≤5) clusters favour the planar structures, but when n=5,they trend to be three-dimensional structure except pure B cluster. Theelectronegativity and absolute hardness of the cluster system was decreased as theOs atomic number m increased, this indicates that the ability of bound electrondecreased, and it’s easier for the electron to transfer. At the infrared spectroscopystudy we found that the local peaks intensity of pure B clusters are much strongerthan that of pure Os clusters obviously. The Os-B hybrid clusters have very few local peaks, except the OsB3cluster. The intensity of the local peak has shown a risingtrend with the atomic number increased.