Photoemission studies of TCNQ compounds

The densities of occupied states of a series of TNCQ compounds have been determined by u.v. photoemission. A clear difference between TCNQ weak charge transfer complexes and anion radical salts including TTF-TCNQ is found. Due to strong electron-molecule coupling narrow delocalized electron bands are not observable.     

Raman spectroscopic studies of LixSiy compounds

The phase diagram of the Li–Si system contains several phases with Li and Si in well defined ratios. So far, only the Raman spectrum of LiSi has been reported. In this work, we present experimental Raman scattering results for the crystalline lithium silicide phases Li₁₂Si₇, Li₇Si₃, Li₁₃Si₄, and Li₂₁Si₅/Li₂₂Si₅, which show clearly distinguishable Raman modes. The experimental results are compared with theoretical data obtained by density functional theory calculations. Copyright © 2013 John Wiley & Sons, Ltd.     

ESCA studies of some niobium compounds

Binding energies of $\text{3d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ level of niobium in some of its compounds have been investigated using X-ray photoelectron spectroscopy. The shift ΔBE in binding energy of $\text{3d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ level of niobium in its several compounds with respect to that in niobium metal can be expressed by the relation ΔBE = i[B_5s + (m ? 1)B_4d], where i and m are the overall ionicity and valence of niobium in a compound.     

Magnetoreflection studies of graphite intercalation compounds

Magnetoreflection spectra are presented for the first time for donor graphite intercalation compounds and for acceptor compounds of low stage. Analysis of these spectra yields values for the K-point effective masses for the conduction and valence bands. Shifts in Fermi level are determined and a breakdown in selection rules for K-point transitions is reported.     

Phase transition studies in polymesomorphic compounds

Summary The structural parameters of theS _A andS _B mesophases and the phase transitionS _G -S _B andS _B -S _A of the compound N-(p-n-octyloxybenzylidene)p-n-butyl aniline were investigated by X-ray diffraction. This work is complementary to the previous structural determination in the crystalline solid phase andS _G phase of the same compound. TheS _B hexagonal lattice parameters atT=66°C area=b=(5.03±0.01) ? andc=(27.6±0.2) ?. TheS _A structural data atT=80°C are layer thicknessd=(26.9±0.2) ? and intermolecular distanceD=(5.04±0.05) ?. The interlayer and the in-plane intermolecular distances were obtained as a function of temperature through all the mesophases. Pretransitional effects were observed at theS _G -S _B phase transition, which corresponds to a progressive reduction to zero of the molecule inclination angle with respect to the normal to the smectic layers. The layer thickness in theS _A phase appeared smaller than that in theS _B due to molecular axial fluctuations. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Electron energy-loss studies of NaxC60 compounds

The crystal and electronic structure of Na_xC₆₀ (4< x < 10) has been investigated using electron energy-loss spectroscopy in transmission. Electron scattering experiments confirm that the crystal symmetry remains face centered cubic over the entire intercalation range. The electronic structure shows a close similarity for the Na₆C₆₀ and Na₄C₆₀ compounds compared to the corresponding K and Rb systems. Upon intercalation to higher stochiometries up to Na₁₀C₆₀ the charge transfer from sodium to C₆₀ turns out to be incomplete, something that has never been observed before in alkali intercalated systems. Current theoretical calculations indicate that this can be understood by taking into account additional states related to the Na atoms in the octahedral site. In Na₁₀C₆₀ the partial filling of the t_1G level of C₆₀ leads to additional electronic transitions near the Fermi energy.     

Optical and resistivity studies of intercalated layer compounds

The optical absorption of three layered compounds has been studied at 4K between 0·1 and 3·0eV. The three compounds, TaS_1·6Se_0·4, TaS_1·6Se_0·4 (pyridine)_1/2, and TaS_1·6Se_0·4 (aniline)_3/4 have layer separations of 6·14, 12·09 and 18·07 A, respectively. Well-defined, free-carrier absorption edges exist near 1.0 eV in all three materials, from which values of the plasma frequency, the interband dielectric constant, and the optical scattering time were derived using the Drude theory. As the layer spacing increases both the plasma frequency and the dielectric constant decrease. The scattering time is short, 3 × 10^?15 sec, and almost independent of layer spacing. The calculated d.c. resistivity is consistent with the measured value in two of the three compounds.The variations of plasma frequency and dielectric constant with layer spacing are successfully interpreted in terms of a simple model which assumes the organic material acts as a dielectric separating metallic layers unchanged by its presence. Although a number of possibilities are put forward, no complete explanation is given for the short relaxation time in these compounds.     

Electrical conduction studies of a series of tetracyanoplatinum compounds

The first experimental study of the electrical conduction properties of a series of tetracyanoplatinum (II) salt single crystals is presented. The results are discussed in conjunction with recent work on the electrical conductivity of KCP. It is shown that there is a systematic variation in the electrical conductivity of the materials with the intrachain Pt-Pt spacing.     

X-ray K-absorption studies ofsome ruthenium compounds

X-ray K-absorption studies of ruthenium in ruthenium metal,RuO₂, K₂(RuCl₆) and K₄[Ru(CN)₆]: 3H₂O have been carried out using 400 mm bent crystal (mica) spectrograph. K-absorption edge of ruthenium in these compounds lies on the higher energy side with respect to that in the ruthenium metal; the divalent K₄[Ru(CN)₆]·3H₂O gives the shift in the range of tetravalent compounds RuO₂ and K₂[RuCl₆]. This discrepancy has been explained on the basis of molecular orbital picture.     

环上双氟取代三联苯类液晶化合物的量子化学研究

运用AM1和PM3两种SCF-MO方法,通过能量梯度全优化计算,给出了对环上双氟取代三联苯类液晶化合物的稳定几何构型、电子结构和生成热、偶极矩、前线分子轨道能级等分子的基本性质.联系有机结构理论进行了分析和讨论.初步阐明了其分子结构与介电各向异性之间的关系,为设计和开发新型液晶分子提供了有较大价值的线索.     

Theoretical studies on a series of nitroaliphatic energetic compounds

Density functional theory calculations at the B3LYP/6-311G＊＊ level are performed to study the geometric and elec- tronic structures of a series of nitroaliphatic compounds. The heats of formation （HOF） are predicted through the designed isodesmic reactions. Thermal stabilities are evaluated via the homolytic bond dissociation energies （BDEs）. Further, the correlation is developed between impact sensitivity h50% and the ratio （BDE/E） of the weakest BDE to the total energy E containing zero point energy correction. In addition, the relative stability of the title compounds is evaluated based on the analysis of calculated Mulliken population and the energy gaps between the frontier orbitals. The calculated BDEs, HOFs, and energy gaps consistently indicate that compound 1,1,1,6,6,6-hexanitro-3-hexyne is the most unstable and the compound 3,3,4,4,-tetranitro-hexane is the most stable. These results provide basic information for the molecular design of novel high energetic density materials.     

Mössbauer effect studies of some trimeric iron compounds

Mössbauer spectra of some basic iron (III) carboxylates are reported. The zero field spectra are quadrupole doublets with a characteristic temperature dependent asymmetry. In applied magnetic fields at 4·2°K large hyperfine magnetic fields are observed. These can only result from a Hamiltonian which is not symmetric in all three sites. This asymmetry may be due to a structural asymmetry or to small intercluster magnetic interactions.     

Solid-state NMR studies of some tin(II) compounds

High-resolution NMR spectra of [Formula: see text] nuclei, particularly (119)Sn and (31)P, in solid tin(II) phosphite, SnHPO(3), and tin(II) phosphate, SnHPO(4), are presented. The results are discussed in relation to the crystal structures. Spinning sideband analysis has been carried out for both nuclei, giving information on the shielding tensors. Satellite peaks allow the indirect Sn,Sn coupling constants to be determined. Surprisingly large values of 2600+/-200Hz and 4150+/-200Hz are reported for SnHPO(3) and SnHPO(4) respectively. The satellite peaks were investigated by using a single Hahn echo for each refocusing time, which showed that the observed splittings result from (119)Sn, (117)Sn coupling. For SnHPO(3), the calculated relative intensities of the satellites for six intra-layer coupling interactions are in agreement with the experiment values, but for SnHPO(4) the coupling appears to be inter-layer in nature. Tin-119 (and in one case phosphorus-31) shielding tensor data derived from MAS NMR are also reported for four other crystalline tin(II) compounds, namely tin diphosphate, tin oxalate, tin sulphate and calcium tin ethylenediamine tetraacetate.     

Trend studies of A15 compounds by self-consistent band calculations

The LMTO (linear muffin tin orbital) method and related canonical methods have been used to achieve self-consistent electronic energy band structures for 26 A15 compounds. Some of the more important results are presented and discussed in terms of density-of-state functions, charge transfer, and superconducting transition temperature.     

XPS studies of ion bombardment damage of iron—sulfur compounds

Chemical reduction on the surface of iron—sulfur compounds due to ion bombardment has been studied by photoelectron spectroscopy (XPS or ESCA). In addition to the “chemical” nature of surface reduction due to excitations and interactions of valence electrons, radiation-induced changes may also involve such factors as ion—surface chemical interactions and the volatilities of the components. Specifically, the data suggest that after ion bombardment, the reduced metallic iron co-exists with the relatively non-volatile elemental sulfur on the surface, in contrast to the loss of the volatile anion components from halogen and oxygen compounds.     

High precision studies of lattice parameter changes in lithium intercalation compounds

We present an in situ X-ray diffraction experiment which measures lattice parameter changes resulting from lithium intercalation to a precision of one part in 10⁵. Experiments on 2H-Li_xTaS₂ demonstrate the sensitivity and reproducibility of the method. To our knowledge, these results are the most precise measurments of lattice parameter changes resulting from intercalation. We find that the c-axis of 2H-Li_xTaS₂ exhibits anomalous behaviour near $\text{x=}\text{1}\text{3}$ and $\text{x=}\text{2}\text{3}$ pr esumably because of the order-disorder transitions in the intercalated lithium.