A density-functional study of Al-doped Ti clusters: TinAl (n=1–13)

Abstract

Equilibrium geometries, stabilities, and electronic properties of TinAl (n = 1-13) clusters have been studied by using density-functional theory with local spin density approximation and generalized gradient approximation. The ground-state structures of TinAl clusters have been obtained. The resulting geometries show that the aluminum atom remains on the surface of clusters for n < 9, but is slowly getting trapped beyond n = 9, meanwhile, the Al atom exhibits a valent transition from monovalent to trivalent. The geometric effects and electronic effects clearly demonstrate the Ti4Al cluster to be endowed with special stability. The studies on the bonds indicate the change from ionic to metalliclike.

Structural, electronic and magnetic effects of Al-doped niobium clusters: a density functional theory study

“…The ground state geometry of Nb 6 Al is C 1 symmetry with the pentagonal Nb 5 a little distorted in comparison with pure Nb 7 structure. The similar shape is found but with higher symmetry for Ti 6 Al(D 5h ) [29], Y 6 Al (C 2v ) [30], Sc 6 Al(C 2v ) [34]. For Al-doped B cluster, the same pentagonal bipyramid structure with C 1 point symmetry is found for B 6 Al, however, for Na 6 Al and Li 6 Al, the structural transition from the Al-capped structure to the Al-encapsulated structure appears at n06.…”

“…It must be pointed out that for pure Nb n clusters only B3PW91 method in conjunction with the LANL2DZ basis set is used for the geometry optimization and vibrational frequency calculation. We will compare the results of Nb n Al with pure Nb n clusters and also compare them with the results for Ti n Al [29], Y n Al [30], Si n Al [31], B n Al [32], Na n Al [33], Sc n Al [34], and Li n Al [35] clusters.…”

“…Another 8c lies higher than 8a by 0.432 eV (B3PW91), 0.338 eV (B3LYP), 0.322 eV (PBEPBE). Several Al-doped clusters, such as Ti n Al [29], Y n Al [30], Sc n Al [34], Pb n Al [35], undergo a structural transition from the Al-capped frame to Al-encapsulated structure at n09, while the structural transition appears prematurely at n06 for Na n Al and Li n Al, and B n Al and Si n Al do not experience the structure transition until n012 and n010, respectively. This is mainly due to the different ionic radii of Al and host atoms and different bond strength of Al-M and M-M bonds.…”

“…Thus structure 2a and 2b are essentially degenerate in energy. Nb 3 Al is the first threedimensional (3D) structure which can be obtained by substituting one Al atom for one Nb atom located at one apex of [29], Y 3 Al(C 3v ) [30], B 3 Al(C 2v ) [32], Sc 3 Al (C 3v ) [34]. Here, it should be mentioned that most of the Nb n Al clusters have relatively low symmetry in comparison with other Al-doped clusters, this can be seen in the following discussion on geometry structures of the Nb n Al clusters.…”

“…Among the doped clusters, the Al atom as an impurity atom has attracted the attention of many researchers [29][30][31][32][33][34][35][36]. Xiang and coworkers [29] studied the equilibrium geometries, stabilities, and electronic properties of Ti n Al (n01-13) using density functional theory, and they concluded that the structural transition takes place at n09. Al atom remains on the surface of clusters for n<9, but is slowly getting trapped beyond n09.…”