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Interfacial Electronic Structure of Thin Cu Films Grown on Ar+-ion Sputter-cleaned a-Al2O3 Substrates

Christina Scheu , Min Gao , Manfred Rühle

The bonding and electronic structure of Cu/(0001)Al2O3 and Cu/(1120)Al2O3 interfaces has been studied experimentally using spatially-resolved transmission electron energy loss spectroscopy. The specimen were prepared by depositing Cu on single-crystal a-Al2O3 substrates, which have been Ar+-ion sputter-cleaned prior to the growth of Cu. For both orientations of the a-Al2O3 substrate, atomically abrupt interfaces formed as determined by high-resolution transmission electron microscopy. The investigations of the interfacial Cu-L2,3, Al-L2,3 and O-K energy loss near-edge structures, which are proportional to the site- and angular-momentum-projected unoccupied density of states above the Fermi level, indicate the existence of metallic Cu-Al bonds at the Cu/Al2O3 interface independent of the substrate orientation.

关键词: Electronic structure , null , null , null

Co对ZrMn2合金贮氢性能影响的第一性原理研究

梁初 , 许灵艳 , 姚春贤 , 蓝志强 , 黎光旭 , 郭进

金属学报

采用基于密度泛函理论(DFT)的平面波赝势(PW-PP)方法，计算了Zr4Mn8-xCox（x=0、2、3）合金及氢化物的电子结构和生成焓。晶胞体积、生成焓的计算值随Co含量的变化趋势与实验测定的相一致。计算结果表明：Zr 4d轨道在费米能级处的态密度、H-Zr(2)与H-Mn(6h)的相互作用强度是决定氢化物稳定性的主要因素；合金Zr4Mn8-xCox的晶胞体积与6h位置原子间相互作用随着Co含量的增加而变化，是影响合金平台氢压的重要因素。

关键词: ZrMn2合金 , Hydrogen-storage property , Electronic structure

Electronic Structure of New Superconducting Perovskite MgCNi3

Li CHEN , Hua LI , Liangmo MEI

材料科学技术（英文）

The electronic structures of new superconducting perovskite MgCNi3 and related compounds MgCNi2T (T=Co, Fe, and Cu) have been studied using MS-Xα method. In MgCNi3, the main peak of density of states is located below the Fermi level and dominated by Ni d. From the results of total energy calculations, it was found that the number of Ni valence electron decreases faster for the Fe-doped case than that for the Co-doped case. The valence state of Ni changes from +1.43 in MgCNi2Co to +3.02 in MgCNi2Fe. It was confirmed that Co and Fe dopants in MgCNi3 behave as a source of d-band holes and the suppression of superconductivity occurs faster for the Fe-doped case than that for the Co-doped case. In order to explain the fact that Co and Fe dopants in MgCNi3 behave as a source of d-band holes rather than magnetic scattering centers that quench superconductivity, we have also investigated the effects of electron (Cu) doping on the superconductivity and found that both electron (Cu) doping and hole (Co, Fe) doping quench superconductivity exist. Comparing with the hole (Co) doping, there was no much difference between Cu and Co doping. This suggests that Co and Fe doping do not act as magnetic impurity.

关键词: Electronic structure , null , null

First-principles calculations of LaNi_5-xSn_xH_y intermetallics and intermediate phase

Dong CHEN , Jingdong CHEN , Yinglu ZHAO , Hailiang HUO , Benhai YU , Deheng SHI

金属学报(英文版) doi:10.1016/S1006-7191(08)60106-4

The crystal and electronic structures of LaNi_4.75Sn_0.25 intermetallics and LaNi_4.5Sn_0.5H_y (y=2.0, 2.5) intermediate phase have been investigated by the full-potential linearized augmented plane wave (FP-LAPW) method. Hydrogen occupation sites in LaNi_4.5Sn_0.5H_y have been determined based on Westlake$'$s criterions: (1) the minimum hole radius is 0.04~nm; (2) the minimum H-H distance is 0.21~nm; as well as geometry optimizations and internal coordinates optimizations. We find that hydrogen atoms prefer to occupy the 12n^*, 6m, 12o, 6m^*sites in LaNi_4.5Sn_0.5H_2.0 and the 6m^*, 4h, 6m, 12o, 12n^* sites in LaNi_4.5Sn_0.5H_2.5. The specific coordinates of hydrogen atoms in LaNi_4.5Sn_0.5H_y are also determined. The results show that hydrogen atoms tend to keep away from tin atoms. The maximum hydrogen content decreases compared with LaNi₅. The interactions between Sn and Ni with H play a dominate role in the stability of LaNi_4.5Sn_0.5-H system. Lattice expansion and increment of Fermi energy E _F show that both Sn and H atoms decrease structural stability of these alloys.

关键词: Rare-earth intermetallics , null , null , null

Geometric and Electronic Structure of Squaric Acid from DFT Calculation

Xuyan XUE , Chunlei WANG , Weilie ZHONG

材料科学技术（英文）

The crystal and electronic structure of antiferroelectric squaric acid is studied using density functional theory method, and the exchange correlation effects are treated by the generalized approximation. In order to understand the ferroelectricity of H2SQ in the molecular plane and the antiferroelectricity in whole crystal, the density of states, charge density distribution and band structure are calculated. The result showed that O2p and C2p play important roles in the interactions between layers. The hybridizations of O2s-H1s and O2p-H1s are responsible for the tendency to ferroelectricity within each layer.

关键词: Antiferroelectricity , null , null