Showing papers on "Lattice constant published in 1981"
TL;DR: In this article, the growth rate of homoepitaxial diamond films reached 1 μm/h at 1000°C; film properties were identical to those of bulk crystals.
981 citations
TL;DR: In this paper, a spinel-type material LiMn2O4 with aqueous acid was found to result in conversion of the spinel to nearly pure MnO2.
846 citations
TL;DR: In this paper, the lattice constants of these compounds were determined and the formation of the Heusler L 2 1 -type phase was compared with model predictions, and it was found that only a limited number of these combinations leads to the cubic L2 1 -Heusler-type compounds.
359 citations
TL;DR: In this paper, the structural perfection of these films has been explored by double crystal x-ray diffraction techniques, which reveal that films of ∼1 μm thick grown at 150 and 220°C are free of low-angle grain boundaries and are exactly lattice matched to the InSb substrate.
Abstract: Heteroepitaxial films on CdTe have been grown by molecular beam epitaxy (MBE) on InSb (001) orientation substrates at growth temperatures ≲220 °C. The structural perfection of these films has been explored by double crystal x‐ray diffraction techniques, which reveal that films of ∼1 μm thick grown at 150 and 220 °C are free of low‐angle grain boundaries and are exactly lattice matched to the InSb substrate. The lattice parameter mismatch is accommodated by misfit elastic strain.
170 citations
TL;DR: In this paper, the lattice parameters and the O/M ratios of the solid solutions between UO2 and trivalent rare earth oxides (RO1.5, R= Y, Gd, Eu or Nd) were investigated.
158 citations
TL;DR: In this paper, single crystals of stoichiometric UO 2 have been irradiated at room temperature with alpha particles emitted from an effectively semi-infinite 238 PuO 2 source to a dose of 3 × 10 16 alphas/cm 2.
138 citations
TL;DR: In this article, a low-temperature X-ray diffraction study was undertaken in order to fix the compositional limit of the tetragonal phase of the Nb-Sn A15 phase.
Abstract: Bulk samples covering the entire homogeneity range of the Nb-Sn A15-phase were prepared by a new method: levitation melting under high argon pressure. The variations of the lattice parameter, superconducting transition temperature, resistivity and critical field slope were measured as a function of composition. A low-temperature X-ray diffraction study was undertaken in order to fix the compositional limit of the tetragonal phase. The theoretical expectations for the critical field slopes at the transition temperature, Tc, based on actually-observed alloy parameters, were found to be in good agreeement with measured values.
137 citations
TL;DR: In this article, the electrical conduction in various phases of the system Bi2O3 (Ln = La, Nd, Sm, Dy, Er, or Yb) was investigated by measuring ac conductivity and the emf of the oxygen gas concentration cell.
133 citations
122 citations
TL;DR: In this paper, the authors present results of direct calculations of structure and lattice dynamics of GaAs using local forms of the ionic pseudopotentials and the density functional, and suggest a possible transition under pressure to an orthorhombic phase, related to the soft $\mathrm{TA}(X)$ phonon.
Abstract: We present results of "direct" calculations of structure and lattice dynamics of GaAs using local forms of the ionic pseudopotentials and the density functional. The predicted lattice constant, bulk modulus, phonon frequencies, effective charges, and Gr\"uneisen parameters agree well with experiment. Eigenvectors at the $X$ point are determined and used to test phenomenological models. We examine anharmonic energies and suggest a possible transition under pressure to an orthorhombic phase, related to the soft $\mathrm{TA}(X)$ phonon.
121 citations
TL;DR: In this paper, the authors re-examined the question of framework ordering in faujasite and proposed new ordering schemes and explained discontinuities in the unit cell constant as a function of composition.
Abstract: The distribution of aluminium and silicon atoms on the tetrahedral sites in synthetic faujasites (zeolites X and Y) has been debated for many years. Although the framework structure of the zeolite is known1, the detailed distribution of Si and Al in the lattice cannot be established by conventional methods, partly because of the very similar scattering powers of silicon and aluminium for X rays and partly because of the difficulties in obtaining crystals of adequate size and perfection. Some inferences have, however, been made on the basis of four indirect approaches: variation of the (cubic) lattice parameter as a function of aluminium content2,3; electrostatic calculations4; change of zeolitic acidity on successive extraction of aluminium from the framework5–7; and the kinetics of crystallization8. All these approaches have assumed the validity of ‘Loewenstein's rule’ which forbids Al atoms from occupying neighbouring tetrahedral sites. High-resolution solid-state 29Si NMR (with magic angle spinning) can determine the detailed Si, Al ordering in zeolites9–16 . NMR coupled with electron diffraction studies has revealed that Loewenstein's rule, generally treated as axiomatic, is broken in Linde A10,13,14 and in at least three other zeolites where Si/Al is nominally unity15. In view of its importance as an archetypal zeolite, particularly commercially, we have re-examined the question of framework ordering in faujasite. We propose new ordering schemes and explain discontinuities in the unit cell constant as a function of composition.
TL;DR: In this article, structural and thermodynamic studies of Kr and Ar adsorbed on Ag(111) were made using low energy electron diffraction, and the phase diagram, lattice constants of the unconstrained monolayer and of the monolayers in equilibrium with the bilayer, latent heats of adsorption and isosteric heats were measured.
TL;DR: In this article, the ground state properties of diamond were investigated using an ab initio density-functional pseudopotential scheme, and the calculated equilibrium lattice constant, cohesive energy, and bulk modulus were in excellent agreement with experiment.
Abstract: The ground-state properties of diamond are investigated using an ab initio density-functional pseudopotential scheme. The calculated equilibrium lattice constant, cohesive energy, and bulk modulus are in excellent agreement with experiment. Unlike Si and Ge, a double hump is found in the valence-electron charge density along the tetrahedral bonds.
TL;DR: In this paper, the structure change with temperature for Fe100-xBx alloys (x=2~33 at.%B) fabricated by a rapid quenching technique has been carried out by measuring magnetization, electrical resistivity and thermal expansion and also by structural analysis by X-ray diffraction.
Abstract: A study of the structure change with temperature for Fe100-xBx alloys (x=2~33 at.%B) fabricated by a rapid quenching technique has been carried out by measuring magnetization, electrical resistivity and thermal expansion and also by structural analysis by X-ray diffraction. The amorphous alloys with 11x13 at.%B transform into α-Fe(B) around 300°C which has a smaller lattice constant than that of α-Fe. Then α-Fe(B) decomposes into two stable α-Fe and Fe2B at about 450°C. For the amorphous alloys with 14x25 at.%B, the amorphous phase transforms into both α-Fe and tetragonal Fe3B compound at about 400°C. With further heating, an orthorhombic Fe3B compound can be observed clearly in addition to these 2 phases for 17x25 at.%B. For temperatures beyond 600~700°C, they transform to the equilibrium phases of α-Fe and Fe2B compound.
TL;DR: A series of mixed metal oxides with pyrochlore structure has been discovered and can be described by the general formula A2[B2−xAx]O7−y where A = Pb or Bi, B = Ru or Ir, 0 < x ≲ 1 and 0 ≤ y ≤ 0.5 as mentioned in this paper.
TL;DR: In this paper, lattice parameter, epitaxial orientation and diffraction intensity measurements for Xe and Kr monolayers on graphite were obtained by transmission high energy electron diffraction (THEED).
TL;DR: In this paper, the relationship between lattice fringe spacing and the lattice parameter is further examined for both uniform and chemically inhomogeneous material, and the techniques described were also applied to an investigation of carbon segregation in residual austenite after the upper bainitic transformation in two steels.
TL;DR: LiInSe 2 single crystals were grown by directional solidification as discussed by the authors, and the lattice constants were determined to be a = 7.218 A, b = 8.441 A, and c = 6.772 A by powder X-ray diffraction.
TL;DR: In this paper, a floating zone technique was used to obtain single crystals with compositions controlled over the nonstoichiometric range (0.75
TL;DR: In this paper, the analysis of the X-ray Debye-Scherrer lines of the fine gold particles of which sizes are in a range from 60 to 230 A, it was found that the thermal expansion coefficient as well as the lattice parameter are not different from those of the bulk crystal, while the characteristic temperature decreases monotonously with the decrease of the particle size.
TL;DR: In this paper, the optical absorption, emission, and excitation spectra for the Eu 5+ ion in the alkali halides have been investigated at room temperature, and it was found that the magnitude of the 10Dq splitting of the 4f 6 5d configuration into its t 2g and e g components caused by the cubic crystalline field follows the spectrochemical series in which the ordering of the halides appears to be determined by the magnitudes of the contact interactions.
Abstract: The optical absorption, emission, and excitation spectra for the Eu 5+ ion in the alkali halides have been investigated at room temperature. It was found that the magnitude of the 10Dq splitting of the 4f 6 5d configuration into its t 2g and e g components caused by the cubic crystalline field follows the spectrochemical series in which the ordering of the halides appears to be determined by the magnitude of the contact interactions. The emission spectrum of the quenched samples consists in all cases of only one band whose peak position moves to shorter wavelengths as the lattice parameter increases within a given series. The excitation spectrum correlates quite well with the optical absorption and shows that the e g level decays to the t 2g from which the fluorescence originates.
TL;DR: In this article, the reconstruction and the relaxation of the (001) surface of Mo and W are studied by using the tight-binding d band and the Born-Mayer repulsive potential.
TL;DR: The lattice constant of polycrystalline, hydrogenated silicon with a mean crystallite size less than 100 A shows an expansion which increases with decreasing size, reaching a limiting value of Δd/d0 ≈ 0.9 − 1.2% as mentioned in this paper.
TL;DR: In this article, the static structural properties of Al are calculated using the self-consistent pseudopotential approach with local density functional expressions for the exchange and correlation energies, the only input parameter is the atomic number.
Abstract: The static structural properties of Al are calculated using the self-consistent pseudopotential approach with local-density functional expressions for the exchange and correlation energies. The only input parameter is the atomic number. Calculated values for the lattice constant, bulk modulus, and cohesive energy agree with experimental values within <1%, approx.1%, and approx.7%, respectively.
TL;DR: In this paper, a neutron scattering study of the structure of films adsorbed on graphite is reported, and the observed two-layer patterns can be indexed with either a pair of incommensurate, triangular-lattice solid layers or a close-packed bilayer.
Abstract: A neutron scattering study of the structure of $^{4}\mathrm{He}$ films adsorbed on graphite is reported. Diffraction from helium monolayers at a temperature of 1.2 K shows the formation of an incommensurate, triangular-lattice solid of high density. As the coverage is increased above two layers, the diffraction pattern changes indicating solidification of a second layer. The observed two-layer patterns can be indexed with either a pair of incommensurate, triangular-lattice solid layers of different densities or a close-packed bilayer; the experimental information available is not sufficient to make a more precise identification. A measurement of the height of the first helium layer above the graphite basal plane was also made. This was done by determining the coverage-dependent shift in the position of the graphite (002) diffraction peak (assumed to arise from interference between film and substrate scattering) and fitting it to a simple structural model. Values for the monolayer height above the graphite plane and for the lattice constants of the possible bilayer structures are given.
TL;DR: In this paper, the crystal structure of Co(IO 3 ) 2 was solved from the Patterson function and a consideration of the structural similarities among the anhydrous 3 d -transition metal iodates.
TL;DR: In this article, the lattice parameter observed at room temperature for the aluminium-rich phase in fully precipitated AlSi alloys has been found to be significantly greater than the expected equilibrium value.
Abstract: The lattice parameter observed at room temperature for the aluminium-rich phase in fully precipitated AlSi alloys has been found to be significantly greater than the expected equilibrium value. This effect increased with silicon content and with annealing temperature. Two possible causes were considered: (i) the difference between the atomic volumes for silicon in the precipitates and in the aluminium matrix; and (ii) the difference between the thermal expansion coefficients of the matrix and the precipitates. A quantitative description is based on the theory of Eshelby developed originally for the case of elastic distortions in a crystal by point imperfections. Distortions due to cause (i) vanished during the anneal. For cause (ii) the theoretical prediction obtained agreed fairly well with the experimental data. The validity of the Eshelby model in this case was discussed. For precipitation studies where the change in lattice parameter is followed, a procedure is proposed to obtain correct soli...
TL;DR: In this article, the bulk modulus of Fe 70 Ni 30, Fe 65 Ni 35 and Fe 72 Pt 28 Invar alloys were obtained by measuring the lattice constants under high pressure up to about 100 kbar using X-ray diffraction technique.
Abstract: The bulk moduli of Fe 70 Ni 30 , Fe 65 Ni 35 and Fe 72 Pt 28 Invar alloys are obtained by measuring the lattice constants under high pressure up to about 100 kbar using X-ray diffraction technique. Large changes in bulk modulus are observed at ferromagnetic to paramagnetic phase transition. The temperature dependence of bulk modulus shows normal behavior both in the ferromagnetic and in the paramagnetic phases of Fe-Ni Invar alloys but shows anomalous behavior in the ferromagnetic phases of Fe 72 Pt 28 alloy. The different behaviors are discussed in connection with thermodynamical relation and the recent theoretical and experimental results.
TL;DR: In this article, the authors measured the pressure dependence of lattice constants usins X-rav diffraction technique and found that the pressure derivative of ω s and the magnetic contribution to the compressibility in Fe-Ni Invar alloy near 0 K are largely different from those in FePt Invar Alloy.
Abstract: Pressure effect on the spontaneous volume magnetostriction ω s of Fe-Ni and Fe-Pt Invar alloys is studied by measuring the pressure dependence of lattice constants usins X-rav diffraction technique. The pressure derivative of ω s and the magnetic contribution to the compressibility in Fe-Ni Invar alloy near 0 K are found to be largely different from those in Fe-Pt Invar alloy. The differences are interpreted phenomenologically in terms of the pressure dependence of T c and M 0 and suggested to relate with the stability of magnetic moment at low temperature.
TL;DR: In this paper, an equation originally derived by Lennard-Jones and Dent for the estimation of Madelung potentials is utilized to study the properties of these potentials within the bulk and at the surfaces of crystals.
Abstract: An equation originally derived by Lennard-Jones and Dent for the estimation of Madelung potentials is utilized to study the properties of these potentials within the bulk and at the surfaces of crystals. It is clear from the equation that potentials at atomic sites only one lattice constant distant from the surface are, in general, indistinguishable from those in the bulk. The equation indicates also that Madelung sums in real space can be so organized as to make them more tractable computationally than they are usually considered to be. Madelung potentials for atomic sites at and near surfaces are obtained for NaCl(100), NaCl(110), CsCl(110), zinc blende (110), wurtzite ($11\overline{2}0$), and rutile (001).