Hybridization,electronic structure and properties of uranium intermetallics: URu3, URh3, UPd3, UIr3 and UPt3

Results of fully-relativistic local density energy band calculations for uranium intermetallics, URu₃ URh₃, UPd₃, UIr₃ and UPt₃, are presented. These include energy bands projected by angular momentum and atom type, total and projected densities of states, specific heat mass enhancement factors and Stoner factors, Systematic variations in hybridization between uranium and transition-metal (X) states,particularly U-f and X-d, are found. The effects of crystal structure on the electronic structure of UPt₃ are examined. The f-d hybridization in the observed hexagonal UPt₃ phase is larger than that in the cubic phase. It is shown by inspecting the wavefunctions on the Fermi surface that the large k-dependence of the hybridization results in strong anistropy of the Fermi surface.     

Modulated magnetic structures of ErPb3, HoPb3, ErTl3 and HoTl3

Neutron diffraction experiments have been carried out on the magnetically ordered phases of ErPb₃, HoPb₃, ErTl₃ and HoTl₃. The magnetic moments were found to be sinusoidally modulated with a propagation vector of (0, 0.2, 0.5) for the Pb-compounds and (0.38, 0.38, 0.16) for the Tl-compounds.Work supported by the Bundesministerium für Forschung und Technologie     

Conformational Analysis of 2, 3, 3-Trimethylhexane

Infrared and Raman spectra were obtained for 2, 3, 3-trimethylhexane and were interpreted with the aid of normal coordinate calculations. It was concluded that this compound exists in three molecular conformations, but a fourth conformer may exist. Vibrational assignments were made for the three conformers.     

Far infrared optical properties of polycrystalline NaClO3, KClO3, NaBrO3 and KBrO3

The resonant frequencies, damping constants and oscillator strengths of far infrared lattice vibrations of polycrystalline NaClO₃, KClO₃, NaBrO₃ and KBrO₃ have been obtained through classical dispersion (CD) analysis of transmission data. Space group analysis has been applied for attribution assignments and to ascertain the translational and rotational character of the respective lattice bands. The damping constants were found to be unusually large indicating short lifetimes of the excited states in spite of an apparent absence of phonon-phonon coupling. The CD analysis of the spectra also provide reliable values of oscillator strength and resonant frequency.     

Dipole properties of PH3, PF3, PF5, PCl3, SiCl4, GeCl4, and SnCl4

Experimental and theoretical photoabsorption cross sections combined with constraints provided by the Kuhn–Reiche–Thomas sum rule, the high-energy behaviour of the dipole oscillator strength density, static dipole polarisabilities, and molar refractivity data when available are used to construct dipole oscillator strength distributions for PH₃, PF₃, PF₅, PCl₃, SiCl₄, GeCl₄, and SnCl₄. The distributions are used to predict dipole sum rules S(k), mean excitation energies I(k), and van der Waals C₆ coefficients.     

Infrared spectra of matrix isolated BH3NH3, BD3ND3, and BH3ND3

The infrared spectra of ammonia-borane, BH₃NH₃, and two of its deuterated isotropic species, BD₃ND₃ and BH₃ND₃, isolated in argon matrix at liquid hydrogen temperature have been measured. Well resolved bands for these three isotopic species have been observed for all the fundamentals. A complete frequency assignment based on C₃v molecular symmetry has been made. A set of force constants have been calculated from the data for the two isotopes BH₃NH₃ and BD₃ND₃ using a valence force field. The agreement between experiment and frequencies calculated from these force constants for the mixed isotopic species, BH₃ND₃, substantiates the present assignment.     

Sphere packing, helices and the polytope {3, 3, 5}

The packing of tetrahedra in face contact is well-known to be relevant to atomic clustering in many complex alloys. We briefly review some of the structures that can arise in this way, and introduce methods of dealing with the geometry of the polytope {3, 3, 5}, which is highly relevant to an understanding of these structures. Finally, we present a method of projection from S₃ to E₃ that enables coordinates for the key vertices of the collagen model of Sadoc and Rivier to be calculated. Received 27 March 2001     

M2, 3 absorption spectra of transition metal ion in MnPS3, FePS3 and NiPS3

Room temperature absorption spectra resulting from the 3p → 3d excitation of transtion metal ions in Mn, Fe and Ni thiophosphates are measured in the photon energy region between 45 and 80 eV. The observed spectral features are well explained by the localized model for the final excited states.     

Relation between electrooptical constants and polar tensors of CH3F,CD3F,CH3Cl,CD3Cl,CH3Br,CD3Br,CD3I,and CD3I

Infrared intensity analysis was done in two ways. In one approach, formulas connecting electrooptical parameters (eop's) and intensities were derived and, using the intensities, the former were obtained. In evaluating the eop's the intensity sum equations were used directly so that the sign ambiguity of $\text{δP}\text{δQ}$ is avoided. In the other method, polar tensors were obtained directly from intensities. The two methods have now been connected, and polar tensors have been obtained in terms of electrooptical parameters so that the former were also free from sign ambiguity of $\text{δP}\text{δQ}$. They compare well with those obtained directly from intensities. In similar connecting formulas by other authors [see, for example, P. L. Prasad, J. Chem. Phys., 69, 4403, (1978)], both polar tensors and eop's were affected by the sign ambiguity.     

The vapour phase Raman spectra,Raman band contour analyses,Coriolis coupling constants,and e-species force constants for the molecules HCF3, ClCF3, BrCF3, and ICF3

The vapour phase Raman spectra of the molecules HCF₃, ClCF₃, BrCF₃, and ICF₃ have been recorded at pressures of up to 1 atmosphere over the fundamental frequency regions. The Raman band contours of the e-species fundamentals have been analysed to yield first-order Coriolis coupling constants from which, together with the fundamental frequencies, e-species force constants of the general harmonic potential function have been evaluated. One force field was found for fluoroform, but two different ones were found for the molecules ClCF₃, BrCF₃ and ICF₃.     

Ab initio model potentials for the alkaline-earth trimers Be3, Mg3, and Ca3

Many-body model potentials for Be₃, Mg₃, and Ca₃ clusters have been constructed with parameters fitted to the corresponding ab initio many-body energy surfaces calculated at the MP4 (SDTQ) level. These ab initio model potentials are accurate over a wide range of atom-atom distances, and are suitable for molecular dynamics simulation, collision dynamics, and other physical applications.     

Pr2O3,Sm2O3,Eu2O3及Dy2O3掺杂SrTiO3的发光光谱

SrTiO_3粉末分别用Pr_2O3、Sm_2O_3、Eu_2O_3以及Dy_2O_3掺杂处理后,以SrTiO_3能吸收的光波(≤387nm)激发后发出的荧光具有稀土离子的发光特征。     

High pressure transport characteristics of Bi2Te3, Sb2Te3, and BiSbTe3

This paper presents ambient and high pressure measurements of transport properties of the Bi₂Te₃–Sb₂Te₃ series of materials. The electrical resistivity, thermal conductivity, and Seebeck coefficient have been measured on both end compounds and the direct solid solution of the two at pressure up to 10 GPa. An additional discussion involving the high pressure structure will be presented. From this, it was determined that these materials undergo at least two structural phase transitions between 0 and 20 GPa and a discussion is presented regarding this and the changes in the transport properties.