First Principles Study Of The Stability Of AlMg_n Clusters And The Magnetic Properties Of AlSc_n Clusters

In this thesis, the first principles calculations are performed to study the geometric structures and electronic properties of AlMgn and BMgn (n=1-12) clusters and the geometric structures, the stablities, and magnetic properties of the AlScn (n=1-8, 12) clusters.Geometry optimization and electronic properties of BMgn, AlMgn (n=1-12) clusters have been studied based on Gaussian 03. With the increase of the atom numbers, the boron atom gradually comes into the bosom of the Mgn clusters. However, the growth patterns of AlMgn clusters are similar to that of magnesium clusters. Doping of one B, Al atom makes the average binding energy higher and the stability enhanced. The atomic motif plays a dominant role in the stability of B, Al atoms doping magnesium clusters. The inducing of B, Al atoms envoys the NBO charge distribution of mainbody magnesium clusters obviously altered. The average NBO chrges distribution of 3p orbital for Mg atoms in AlMgn clusters is in agreement with the stability of AlMgn (n=1-12) clusters.Equilibrium geometrical, electronic, and magnetic properties of small ScnAl (n=1–8,12) clusters have been studied based on the DFT with all-electron spin-polarized generalized gradient approximation with Dmol3. The calculated results show that the Al atom remains on the surface for n=1–8, but at the center of the Sc12Al cluster with a variable icosahedral structure (C3v). Doping of the Al atom enhances the stability of the scandium clusters. Maximum peaks are observed for clusters of n=3, 6 on the size dependence of the second-order energy differences and fragmentation energies, implying that the two clusters possess relatively higher stability. This study also reveals that the Al atom is seen to induce significant changes in the magnetic property of the host cluster. Especially, the magnetic moment of the ScnAl cluster is quenched for n=3, 5, and 7, and the total magnetic moment of the Sc12Al cluster is only 7μb (but 19μb for Sc13).