Structural Properties Of B_nTi Clusters And Hydrogen Storage Behavior Of Y Coated Si@Al₁₂ Clusters

In this thesis, we investigate the geometric, electronic and magnetic of B_nTi (n=1-12) clusters and hydrogen molecules adsorption on Y coated Si@Al₁₂ cluster using the generalized gradient approximation (GGA) density functional theory. The main contents are presented as the followings:The ground-state structures, electronic and magnetic properties of B_nTi (n=1-12) clusters were systematically studied with the generalized gradient approximation based on the density functional theory. Results reveal that the ground-state structures for the small B_nTi clusters favor planar or quasi-planar structures, while starting from n=6, the three-dimensional structure with most Ti-B bonds dominates the growth pattern. The calculated second-order energy difference manifests that the magic numbers of stability are 3, 7, 10 for the B_nTi clusters. The results of Mulliken population analysis indicate that there is the charge transfer from Ti to B site and the coexistence of ionic and covalent bonding characteristics. The total magnetic moments of the B_nTi clusters range from 0 to 2μB except the BTi (5μB) clusters, and are mainly provided by the 3d orbital of Ni atom and some B atoms. The magnetic moment of the B atoms in B₃Ti and B₇Ti clusters exhibits the antiferromagnetic alignment.The adsorption property of hydrogen molecules on Y_mSi@Al₁₂ (m=1-3) cluster was investigated using density functional theory. The results show that yttrium atoms do not suffer from clustering on the Si@Al₁₂ cluster. 18-electron rule can be used to design these systems, and Si@Al₁₂ cluster coated with three yttrium atoms can adsorb 16 H₂ molecules with gravimetric density of up to 5.0 wt%. The calculated adsorption energy of 0.324～0.527 eV/H₂ molecule is suited for reversible hydrogen storage at near ambient conditions.