X-ray emission spectra and chemical bonding in TiC,TiN and TiO

The experimental X-ray emission spectra of titanium carbide, nitride and oxide have been obtained. Quantum-chemical calculations of the electronic structure of clusters in TiC, TiN and TiO have been carried out by the semiempirical Mulliken-Wolfsberg-Helmholtz method with self-consistency on charges and configurations. The results of these calculations are in good agreement with the X-ray spectroscopy data and offer a reasonable explanation of the experimental spectra. Chemical bonding and electronic structure of the compounds are discussed. Ionicity is shown to increase from TiC to TiO according to the electronegativity principle, the calculated charges on the metal ions being close to experimental estimates. The role of metal-metal and metal-nonmetal interactions in the chemical bonding is analysed. Vacancy models for TiO and their effect on the X-ray emission spectra are investigated. By the CNDO method with configurational interactions the optical spectrum of titanium carbide has been calculated. It is shown that this spectrum may be interpreted from the results for the [TiC₆] cluster, without introducing the Lye-Logothetis band scheme with negative charge on the metal ion.     

系列异金属类立方烷原子族化合物的振动光谱

通过振动光谱和Ｘ－射线结构分析数据的结合,归属了系列具有「Ｍ３ＹＳ３Ｍ′」（Ｍ＝Ｍｏ,Ｗ;Ｙ＝Ｏ,Ｓ;Ｍ′＝Ｃｕ,Ｓｎ,Ｓｂ,Ｐｂ,Ｂｉ）簇芯的异金属四核类立方烷原子簇化合物的主要振动谱峰。讨论了五种结构类型的光谱特征和成键状态,Ｍ′的加入使ｖＭ－（μ３－Ｙ）和ＶＭ－ｓ频率下降。当Ｍ′为过渡金属,例如Ｃｕ时,Ｃｊ与「Ｍ３ＹＳ３」结合紧密造成了Ｃｕ－Ｓ共价键相当的ｖＣｕ－ｓ振动频率,而当Ｍ′为主族金属时,ＶＭ′－ｓ远小于相应共价键的振动频率值。文中还对ｖＭ－Ｍ振动进行若干论述。     

Ionic monolayers on metals: II. neutral mixed layers and surface reconstruction

Mixed layers of ions on a metal crystal surface are important in adsorption and corrosion. We consider reconstructed periodic layers on Ni, and use a modified Born-Haber cycle to make semi-quantitative estimates of heats of adsorption. For O, S, and Se atoms in neutral mixed layers on the (100) and (111) Ni planes, our estimated heats of adsorption have the right sign and magnitude if ionic charges are large. We make the novel suggestion that negative Ni ions are important in some of the structures. Also, we propose a new distinction between reconstruction and true corrosion, and we conclude that metal-metal bonding is the characteristic feature of reconstructed layers. We summarize our findings with a brief comparison of ionic layers of the two kinds.     

Density functional calculations on 13-atom Pd12M （M= Sc-Ni） bimetallic clusters

The geometric structures,electronic and magnetic properties of the 3d transition metal doped clusters Pd12M(M=Sc-Ni) are studied using the semi-core pseudopots density functional theory.The groundstate geometric structure of the Pd12M cluster is probably of pseudoicosahedron.The Ih-Pd12M cluster has the most thermodynamic stability in five different symmetric isomers.The energy gap shows that Pd12M cluster is partly metallic.Both the absolutely predominant metal bond and very weak covalent bond might exist in the Pd12M cluster.The magnetic moment of Pd12M varies from 0 to 5 μB,implying that it has a potential application in new nanomaterials with tunable magnetic properties.     

Electronic structure of carbon nanotubes modified by alkali metal atoms

The electronic structure and parameters of the energy band structure of (n, 0)-type nanotubes modified by alkali metal atoms (Li, Na) and intercalated by potassium atoms are studied. The quantum-chemical semiempirical MNDO method and a model of the covalent cyclic cluster built in via ionic bonding are used to model infinitely long nanotubes. The electronic density of states of modified nanotubes is found. It is shown that semiconductor-metal transitions can occur in semiconductor nanotubes and that semimetal nanotubes can undergo metal-metal transitions.     

Photoelectron spectroscopy of size-selected cluster ions using synchrotron radiation

A new experimental setup for photoelectron spectroscopy of size-selected cluster ions using synchrotron VUV radiation as generated by the Swiss Light Source is presented. An intense positively charged cluster ion beam is produced in a high-intensity magnetron sputter source. The clusters are subsequently mass selected in a sector magnet. To maximize the residence time of the cluster ions in the ionization region of the velocity map imaging spectrometer, the cluster ion beam is decelerated where it crosses the light beam. First experiments on (MoO₃) _n ⁺ (n = 69 and 59) cluster cations show that the approach is capable of delivering photoelectron spectra of size-selected transition metal cluster ions.     

过渡金属富勒烯化合物V_xC_(60)的Raman光谱

研究了金属富勒烯化合物 Vx C6 0 的 Raman光谱。通过比较不同金属原子含量 ( x=1 .44,2 .65,4.35,1 1 .2 )样品的 Raman光谱 ,发现过渡金属 V的原子与 C原子之间出现键合。当金属含量较高时 ,这种碳笼结构的金属富勒烯化合物转变为金属碳化物。     

卷积差方法在过渡金属离子EPR谱中的应用

用卷积差方法提高EPR谱的分辨率,可以从多种过渡金属离子的迭加谱中直接测量出不同离子的波谱参数a_R、a_⊥、g_R和g_⊥,该方法还可提高各向异性g因子的测量精度.     

铝对过渡金属离子掺杂的二氧化硅溶胶凝胶玻璃发光性质的影响

用溶胶凝胶法制备了过渡金属离子(Ni2+,Mn2+和Cu2+)单掺、铝共掺的二氧化硅玻璃,测量了荧光光谱、吸收光谱和红外光谱,研究了Al3+对过镀金属离子在二氧化硅玻璃中发光性质的影响。研究结果表明,Al3+对过渡金属离子的发光性质有着显著影响:Ni2+,Mn2+和Cu+的发光强度大幅度提高,Mn2+的发光峰峰位改变。     

Band structure calculations on the layered compounds FeGa2S4 and NiGa2S4

For the compounds FeGa₂S₄ and NiGa₂S₄ band structure calculations have been performed by the ab initio plane wave pseudo-potential method. The valence charge density distribution points to an ionic type of chemical bonding between the transition metal atoms and the ligand atoms. Two models for the pseudo-potentials are used to calculate the band structures: (a) only s and p electrons and (b) also the d-shells of the transition metal atoms are included in the pseudo-potentials. The differences between these two cases of band structures are discussed. Energy gap formation peculiarities are analysed for both crystals. Zak's elementary energy band concept is demonstrated for the energy spectra of the considered crystals.