Chen Yu-Hong

First-Principle Study of H2 Adsorption on Mg3N2(110) Surface

The adsorption of H2 on two kinds of Mg3N2(110) crystal surface is studied by first principles. Adsorption sites, adsorption energy, and the electronic structure of the Mg3N2 (110)/H2 systems are calculated separately. It is found that H2 is mainly adsorbed as chemical adsorption, on these sites the H2 molecules are dissociated and the H atoms tend to the top of two N, respectively, forming two NH, or the H atoms tend to the same N forming one NH2. There are also some physical adsorption sites. One of the bridge sites of Mg3N2(110) surface is more favorable than the other sites. On this site, H atoms tend to the top of two N, forming two NH. This process belongs to strong chemical adsorption. The interaction between H2 molecule and Mg3N2(110) surface is mainly due to the overlap-hybridization among H 1s, N 2s, and N 2p states, covalent bonds are formed between the N and H atoms.

Structures and electronic properties of SimN8-m(0 < m < 8) clusters: a density functional theory study

The geometries, electronic structures and related properties of SimN8-m(0 < m < 8) clusters are studied using density functional theory (DFT) with hybrid functional B3LYP. The calculated results reveal several trends. For any stoichiometric clusters, the lowest energy isomers with an alteration of N and Si atoms are favourable in energy if the numbers of Si and N atoms are large enough to form ... Si–N–Si–N... alternative chains. The bond lengths of single Si–N bonds are very close to the corresponding values of the bulk and other Si–N clusters. The geometries for N-rich and Si4N4 clusters are planar structures, but three-dimensional structures are favourable in energy for Si-rich clusters. With the increase of m, the isotropic polarizability and average polarizability increase, the total binding energies generally decrease, the HOMO-LUMO gap and vertical ionization potential oscillate with increasing number of valence electrons, and their values with even valence electrons are larger than those with odd valence electrons. The atomic charges, IR and Raman properties are also reported.

Effect of a magnetic field on the energy levels of donor impurities in the ZnO parabolic quantum well

Energy levels of a donor impurity in the ZnO parabolic quantum well under the magnetic field are investigated using the variational method. The binding energy of the ground state, the energies of 2p± state and 1s ! 2p transition energies of a hydrogenic donor in the ZnO parabolic quantum well are numerically calculated as a function of the strength of magnetic field for different parabolic potential fields. The results show that the external magnetic field has an obvious influence on the binding energies and the 1s ! 2p transition energies of a hydrogenic donor. The 1s to 2p transition energy increases linearly with the strength of magnetic field, but the 1s to 2p transition energy decreases when the strength of magnetic field increases for the small field strength. Compared to the GaAs parabolic well, the donors are more tightly bound to the ZnO parabolic well and the influence of external magnetic field on the binding energy of a donor is much stronger in the ZnO parabolic well.