Xide Xie

Electronic structure and magnetic properties of δ-MnGa

Abstract The electronic structure and magnetic properties of δ-MnGa are studied by using the self-consistent linearized augmented plane-wave (LAPW) method. The analyses from the band structure, the density of states, total energy and the magnetic moments show that the ground states of the unstrained and strained δ-MnGa are in ferromagnetic phases, and the magnetic structures are affected significantly by strain.

Mn chemisorption on a GaAs(001) surface

The chemisorption of a Mn adatom on a GaAs(001) surface is studied by using the charge self-consistent extended Huckel method and a cluster model. Mn adatom chemisorption on the Ga face and As face are considered separately. The binding energy, site preference and the electronic structure of a Mn adatom on the GaAs(001) surface are studied in detail. As the initial stage, the results obtained in this paper are in qualitative agreement with the experimental results. The different preferred sites for the adatom Mn on the Ga face and As face can, to some extent, help us to understand the different structures of MnGa film and MnAs film on the substrate GaAs(001).

Electronic Structural Properties of β-C3N4, β-Si3N4 and β-Ge3N4

The electronic energy bands of a series of β-phases of carbon nitride, silicon nitride and germanium nitride have been calculated using a first-principle linear combination of muffin-tin orbital method with the atomic-sphere approximation (LMTO-ASA). The band gaps obtained for the three compounds are 4.18, 5.18 and 4.03 eV, respectively. For β-C 3 N 4 , the nitrogen 2p orbitals play an important role in the top of the valence band (VB) due to its non-bonding character. For β-Si 3 N 4 , the silicon 3d orbitals play an important role both in the VB and in the conduction band (CB). Its band gap is indirect which is in agreement with other calculated results. For β-Ge 3 N 4 , the germanium 4d empty orbitals play a role analogous to 3d of Si in β-Si 3 N 4 . Its 3d orbitals preserve the characteristics of atomic orbitals and give very little contributions to other VBs and the CB. This is the first theoretical study reported on the electronic structure of β-Ge 3 N 4 .

Chemisorption of Mn on a GaAs(110) surface

The chemisorption of Mn on a GaAs(110) surface is studied theoretically by using a cluster model. The site preference for a Mn adatom is determined, and the electronic structure of the adsorbate system is calculated. It is shown that, instead of being adsorbed above the surface, the deposited Mn atom prefers to substitute a surface Ga atom. It is also found that the surface As atoms which are bonded to the Mn atom have only a weak interaction with the Ga atom which is being replaced. With increasing Mn coverage, these displaced Ga atoms may become randomly distributed over the surface. Our theoretical results are consistent with the experimental measurements. The reason for the occurrence of atom substitution is analyzed in detail.

Density-functional studies of magnetic and electronic structures for the perovskite oxides LaMn1−xCrxO3

The magnetic and electronic properties of the Mn-site-doped perovskite oxides LaMn1-x Crx O3 (x = 0.0, 0.25, 0.5, 0.75, 1.0) are studied theoretically by using the tight-binding linear muffin-tin orbital method. Rather than ferromagnetic structures, ferrimagnetic ones of a certain type are found to be the most stable states for compounds with intermediate doping levels; this is related to the strong positive Mn3+ -Mn3+ interaction and negative Cr3+ -Cr3+ interaction. The reasons for there being these two kinds of interaction are analysed. The total magnetic moments for the doped compounds increase with x varying from 0.0 to about 0.25; this is in good agreement with experimental results. For the doped compounds with x = 0.5 and 0.75, in addition to the distorted orthorhombic structures, the cubic structure has also been studied. In addition to being found for the doped compound with x = 0.5 (with interlacing-type doping), half-metallic bands have also been found for the doped compound with x = 0.75 both with ferromagnetic and ferrimagnetic (in several types) interaction.

Theoretical studies of CO and NO on CuO and Cu2O(110) surfaces

Abstract The characteristics of CO and NO adsorption on surfaces of CuO(110) and Cu 2 O(110) have been studied by using the self-consistent-charge discrete variational X a method (SCC-DV-X a ). The calculated results show that the CO and NO molecules are perpendicularly adsorbed on cuprous ions of Cu 2 O and cupric ions of CuO, respectively and with oxygen pointing upward in both cases. The order of chemisorption energy of the four adsorbed systems is: CuO-NO > Cu 2 O-CO > Cu 2 O-NO > CuO-CO. In all chemisorptions discussed d orbitals of Cu do play an important role.

Theoretical Studies of Electronic and Magnetic Properties of Mn-Site-Doped Perovskites LaMn1–xNixO3

The electronic and magnetic properties of the Mn-site-doped perovskite oxides, LaMn 1-x Ni x O 3 (x = 0.0, 0.25, 0.5, 0.75, 1.0) are studied theoretically by using the tight-binding linear-muffin-tin orbital (TB-LMTO) method. Metallic bands have been found for compounds with intermediate doping levels as well as for the two end members LaMnO 3 and LaNiO 3 . Compounds with the doping level 0.25 ≤ x ≤ 0.5 have ferromagnetic ground states; for the 0.75 doped compound, ferrimagnetic phase is obtained, although the ground state of LaMnO 3 and LaNiO 3 is the antiferromagnetic and paramagnetic phase, respectively. There is no distinct charge redistribution found on the Mn and Ni ions in the doped compounds, compared with that in the two end members. The total magnetic moments for the compounds decrease with x increasing from 0.3 to 1.0, which is in good agreement with experimental results. The reasons of the decrease of total moments with x are analyzed in the present work.

Surface Magnetism of One Monolayer Mn Atoms on GaAs(001) Surface

The surface magnetism of one monolayer Mn atoms on GaAs(001) surface is studied by the self-consistent tight-binding linear muffin-tin orbital method. It is found that the magnetic ordered phases (ferromagnetic and antiferromagnetic) are more favorable than the paramagnetic one, the density of states peak far below the Fermi level observed in synchrotron radiation photoemission study has been identified as due to the contribution of Mn 3d majority states.

Theoretical Study of Structural and Electronic Properties of Sodium in Zeolitic Cage

The structural and electronic properties of sodium adsorbed in the β-cage of zeolite A have been studied by using the extended Huckel method and cluster model. The β-cage, which consists of Si 12 Al 12 O 48 , is one of the structural units of zeolite A. The site preference for a Na adatom and several stable configurations for Na adatoms in the β-cage have been determined and the electronic structures of the systems are investigated. It is found that instead of forming metal clusters the Na adatoms prefer to be adsorbed separately at adsorption sites I or II which are located near the center of the hexagonal face (site I) and on the square face (site II) in the β-cage, respectively. The result is reasonable from the fact that the adsorbed Na atoms are almost ionized so that the Coulomb repulsion prevents them from forming clusters at short distances. The electronic structures show that the peak near the Fermi level increases obviously after the incorporation of sodium atoms into the β-cage. A new peak which is near the first ionization energy (5.14 eV) of Na atom appears when the numbers of Na atoms adsorbed by the β-cage are larger than twelve.