Yang Zongxian

Coadsorption of gold with chlorine on CeO2 (111) surfaces: A first principles study

To investigate the effects of chlorine on the Au/ceria catalysts, the adsorption of gold or chlorine and their coadsorpiton on the stoichiometric and partially reduced CeO2 (111) surfaces are studied from the first principles. It is found that the adsorption of Au is significantly enhanced by the chlorine preadsorption on the stoichiometric CeO2 (111) surface; while on the partially reduced CeO2 (111) surface, the preadsorbed chlorine inhabits the oxygen vacancy (which is the preferred adsorption site for gold), leading to a CeOCl phase and the dramatical weakening of the Au adsorption. Therefore, chlorine on the CeO2 (111) surface can affect the Au adsorption thus the activity of the Au/CeO2 catalyst.

First principles study of the magnetism driven by cation defects in CeO2: the important role of O2p states

The magnetism driven by cation defects in undoped CeO2 bulk and thin films is studied by the density functional theory corrected for on-site Coulomb interactions (DFT+U) with U = 5 eV for the Ce4f states and U = 7 eV for the O2p states. It is found that the Ce vacancies can induce a magnetic moment of the ~ 4 μB/supercell, which arises mainly from the 2p hole state of the nearest neighbouring O atom (~ 1 μB on per oxygen) to the Ce vacancy. The effect of the methodology is investigated, indicating that U = 7 eV for the O2p state is necessary to obtain the localized O2p hole state in defective ceria with cation vacancies.

First-Principles Studies for the Electronic Structures of Diluted Magnetic Semiconductors (Ga, Fe)As*

First-principles LMTO-ASA band calculations are performed for Ga1-xFexAs (x=1, 1/4, 1/8) by assuming supercell structures. It is found that the antiferromagnetic (AFM) state is stable for x=1/4. For x=1/8, ferromagnetic (FM) state is more stable than AFM state, and no stable magnetic state exists for x=1. In both the cases the magnetic moments of As and Ga atoms are parallel to those of the nearest Fe atoms due to the p-d hybridization. Further, the band structure shows rather localized Fe 3d state in the gap, and the parallel polarization is confined rather in the vicinity of Fe site.

Surfactant Effects of Au on Polar ZnO Surfaces

The electronic properties of one monolayer of Au atoms on polar ZnO surfaces are examined by first-principles slab calculations. It is found that an Au ad-layer on top of the surface is energetically more favourable than other gold diffused cases, and Au capping layer on the ZnO polar surfaces may modify the growing properties of ZnO nanostructures by enhancing the binding energy.