Li-Xia Zhao

Ultra-high hydrogen storage capacity of Li-decorated graphyne: A first-principles prediction

Graphyne, consisting of sp- and sp2-hybridized carbon atoms, is a new member of carbon allotropes which has a natural porous structure. Here, we report our first-principles calculations on the possibility of Li-decorated graphyne as a hydrogen storage medium. We predict that Li-doping significantly enhances the hydrogen storage ability of graphyne compared to that of pristine graphyne, which can be attributed to the polarization of H2 molecules induced by the charge transfer from Li atoms to graphyne. The favorite H2 molecules adsorption configurations on a single side and on both sides of a Li-decorated graphyne layer are determined. When Li atoms are adsorbed on one side of graphyne, each Li can bind four H2 molecules, corresponding to a hydrogen storage capacity of 9.26 wt. %. The hydrogen storage capacity can be further improved to 15.15 wt. % as graphyne is decorated by Li atoms on both sides, with an optimal average binding energy of 0.226 eV/H2. The results show that the Li-decorated graphyne can s...

Magnetic superatoms in VLi(n) (n = 1-13) clusters: a first-principles prediction.

We demonstrated a first-principles investigation to search for magnetic superatoms in the vanadium-doped lithium clusters VLi(n) (n = 1-13). The stabilities of VLi(n) clusters were determined through geometrical and electronic optimizations. It is found that the growth pattern of VLi(n) in 3-space follows adding a Li atom capped on VLi(n-1) clusters. All doped clusters show larger relative binding energies compared with pure Li(n+1) partners and display tunable magnetic properties. When n = 8-13, the VLi(n) clusters adopt a cage-like structure with an endohedral V atom and are identified as superatoms with their magnetic moments successively decreasing from 5 to 0 μB. The isolated VLi8 superatom is emphasized due to its robust magnetic moment as well as high structural and chemical stability analogue of a single Mn(2+) ion. Molecular orbitals analysis shows that VLi8 has an electronic configuration of 1S(2)1P(6)1D(5), exhibiting Hunds filling rule of maximizing the spin-like atoms. Electronic shell structures of 1S(2) and 1P(6) are virtually unchanged in Li9 cluster as the V atom substitutes for the embedded Li atom, indicating that the electron-shell-closing model is valid for explaining its structures and stabilities. The results show that the tailored magnetic building blocks for nanomaterials can be formed by seeding magnetic dopants into alkali metal cluster cages.

Unraveling Special Structures and Properties of Gold-Covered Gold-Core Cage on Au33-42 Nanoparticles.

New low-energy atomic structures and properties of medium-size gold nanoparticles (Au33-42) are studied, where the atomic positions of gold atoms are obtained on the basis of the generic formulation of shell and core concept. Hollow cage, tube-like, double-layered flat, fcc-like, and close-packed configurations are predicted. Relativistic density functional theory optimization indicated that low-symmetry stuffed configurations are all lower in energy than the others. Further analysis of the optimized structures of Au33-42 nanoparticles shows that these gold cores are all four-atom tetrahedral structures and similar to each other; only the number and positions of gold atoms at the surface of gold core are different. Compared with structure and electronic properties, Au33-42 nanoparticles have different structure stabilities and chemical activities. But they are all hybridizations of sp and d electrons. The obtained information forms the basis for future chemisorption studies to unravel the catalytic effects of gold nanoparticles.