Showing papers on "Lattice constant published in 1984"
TL;DR: In this paper, the authors derived an expression for the total energy of a metal using the embedding energy from which they obtained several ground-state properties, such as the lattice constant, elastic constants, sublimation energy, and vacancy-formation energy.
Abstract: We develop the embedded-atom method [Phys. Rev. Lett. 50, 1285 (1983)], based on density-functional theory, as a new means of calculating ground-state properties of realistic metal systems. We derive an expression for the total energy of a metal using the embedding energy from which we obtain several ground-state properties, such as the lattice constant, elastic constants, sublimation energy, and vacancy-formation energy. We obtain the embedding energy and accompanying pair potentials semiempirically for Ni and Pd, and use these to treat several problems: surface energy and relaxation of the (100), (110), and (111) faces; properties of H in bulk metal (H migration, binding of H to vacancies, and lattice expansion in the hydride phase); binding site and adsorption energy of hydrogen on (100), (110), and (111) surfaces; and lastly, fracture of Ni and the effects of hydrogen on the fracture. We emphasize problems with hydrogen and with surfaces because none of these can be treated with pair potentials. The agreement with experiment, the applicability to practical problems, and the simplicity of the technique make it an effective tool for atomistic studies of defects in metals.
5,912 citations
TL;DR: In this paper, a new compound composed of Nd, Fe, and a small quantity of B (about 1 wt. %) has been found, which has a tetragonal structure with lattice constants a=0.880 nm and c=1.221 nm.
Abstract: A new compound composed of Nd, Fe, and a small quantity of B (about 1 wt. %) has been found, which has a tetragonal structure with lattice constants a=0.880 nm and c=1.221 nm. This phase, which has the approximate composition, 12 at. % Nd, 6 at. % B and balance Fe, possesses remarkable magnetic properties. From the approach to saturation an anisotroy constant of about 3.5 MJ/m3 can be calculated, while saturation magnetization amounts to 1.35 T. The magnetization versus temperature curve shows a Curie temperature of 585 K, which is much higher than those of the Fe and light rare earth binary compounds. Based on the new compound, sintered permanent magnets have been developed which have a record high energy product. Permanent magnet properties and physical properties of a typical specimen which has the composition Nd15B8Fe77 are as follows: Br =1.23 T, HcB =880 kA/m, HcI =960 kA/m, (BH)max =290 kJ/m3, temperature coefficient of Br =−1260 ppm/K, density=7.4 Mg/m3, specific resistivity=1.4 μΩm, Vickers hardn...
2,525 citations
TL;DR: In this paper, the lattice parameter of high-purity silicon is measured as a function of temperature between 300 and 1500 K, and the linear thermal expansion coefficient is accurately determined.
Abstract: The lattice parameter of high‐purity silicon is measured as a function of temperature between 300 and 1500 K, and the linear thermal expansion coefficient is accurately determined. Precise measurements are made by the high‐temperature attachment for Bond’s x‐ray method to a few parts per million. It is found that the temperature dependence of the linear thermal expansion coefficient α(t) is empirically given by α(t)=(3.725{1−exp[−5.88×10−3{(t−124)} +5.548×10−4t)×10−6 (K−1), where t is the absolute temperature ranging from 120 to 1500 K. It is shown that the lattice parameter in the above temperature range can be calculated using α(t) and the lattice parameter at 273.2 K (0.5430741 nm). Measured values of the lattice parameter and the thermal expansion coefficient for high‐purity float‐zoned (100 kΩ cm) and Czochralski‐grown (30 Ω cm) single crystals are uniformly distributed within ±1×10−5 nm and ±2×10−7 K−1 with respect to the values obtained from the above empirical formula.
1,089 citations
TL;DR: In this article, the lattice constants and the X-ray density of ternary tetragonal compounds of the composition R 2 Fe 14 B were determined for R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu.
249 citations
TL;DR: The van der Waals epitaxy can be realized in the materials having no dangling bonds on their clean surfaces, on which epitaxial growth proceeds by the van derWaals force as mentioned in this paper.
219 citations
TL;DR: In this paper, the difference in lattice parameter between the silicon substrate and the porous layer and the strains of the porous lattice have been determined accurately on a double crystal diffractometer for a series of porous structures.
197 citations
TL;DR: In this article, the graphitic phases of C and Si were studied with the use of the pseudopotential local density functional approach, and good agreement with experiment was obtained for the in-plane lattice constant, interlayer spacing, isotropic bulk modulus, and graphite-diamond structural energy difference.
Abstract: The graphitic phases of C and Si are studied with the use of the pseudopotential local-density-functional approach. For graphite, good agreement with experiment is obtained for the in-plane lattice constant, interlayer spacing, isotropic bulk modulus, and graphite-diamond structural energy difference. Graphitic Si has relatively weak bonding and its formation is unlikely since its energy is 0.71 eV/atom higher than the diamond phase and a large negative pressure of -69 kbar is required.
182 citations
TL;DR: In this paper, the high pressure behavior of the structural and electronic properties of MgO was examined with use of the pseudopotential method within local density theory, and it was shown that the CsCl phase for MgOs is unlikely to exist even in the lower mantle of the Earth.
Abstract: The high-pressure behavior of the structural and electronic properties of MgO is examined with use of the pseudopotential method within local-density theory. At zero pressure the rocksalt phase is found to be lower in energy than a hypothetical CsCl structure. However, we predict a phase transformation into an insulating CsCl structure at a very high hydrostatic pressure of about 10 Mbar. This result predicts that the CsCl phase for MgO is unlikely to exist even in the lower mantle of the Earth. The calculated ground-state properties such as lattice constant, bulk modulus, and cohesive energy for the rocksalt phase are in good agreement with experiment. The electronic band structures at normal and high pressures are also given.
163 citations
AT&T1
TL;DR: In this article, the pseudopotential local density functional approach was used to calculate the lattice constant, the $x$ parameter for atomic coordinates, and the phonon frequency for the Si-III (BC-8) crystal phases of Si and Ci.
Abstract: With use of the pseudopotential local-density-functional approach, the lattice constant, the $x$ parameter for atomic coordinates, and the phonon frequency of the mode ${\ensuremath{\Gamma}}_{1}^{+}$ are calculated for the Si-III (BC-8) crystal phases of Si and Ci. The results agree well with available experimental data for the BC-8 phases of Si. From the total-energy curves of the diamond and the BC-8 phases of Si, we find that the BC-8 phase of Si is not stable at ambient pressure or at high pressure. The diamond---BC-8 (I-III) transition of Si will not occur quasistatically. Comparing the diamond, the BC-8, and the simple-cubic phases of C, we find that diamond will first transform to the BC-8 phase at 12 Mbar and then to the simple-cubic phase at 27 Mbar under quasistatic conditions.
152 citations
TL;DR: In this paper, a model of the microscopic structure of the zinc-blende-type A1-xBxC ternary alloys based on a random distribution of cations has been developed.
Abstract: The nearest-neighbor distances around Te atoms in the random semiconducting alloy Cd1-xMnxTe have been determined by the extended x-ray-absorption fine-structure technique. The distribution of the anion-cation distances is bimodal. A model of the microscopic structure of the zinc-blende-type A1-xBxC ternary alloys based on a random distribution of cations has been developed. The model describes the bimodal distribution of nearest-neighbor distances in terms of distortion of the anion sublattice, using only the lattice constant of the alloy and the bond-stretching constants of each binary component. Within the framework of this model we consider also the problem of the structural stability of Cd1-xMnxTe.
138 citations
TL;DR: In this paper, the authors examined the structural characteristics of delithiated LiVO2 prepared by chemical and electrochemical methods and examined by powder X-ray diffraction techniques, showing that removal of lithium from the layered LiVO 2 structure (space group = R 3 m ) results in a rearrangement of the vanadium ions in the cubic-close-packed oxygen lattice.
TL;DR: In this article, X-ray lattice parameter measurements and Rietveld refinements of neutron diffraction data were used to evaluate intracrystalline cation distributions and their variation with quenching temperature.
TL;DR: In this paper, the effect of tungsten and carbon additions on the lattice parameter, crystallographic structure, magnetic saturation, and tensile properties of cobalt alloys was investigated.
TL;DR: In this paper, a set of superlattices of the dilute magnetic semiconductor Cd1−x Mnx Te (x∼0.2) alternating with CdTe have been successfully grown for the first time using the molecular beam epitaxy technique.
Abstract: Single‐crystal multilayers of the dilute magnetic semiconductor Cd1−x Mnx Te (x∼0.2) alternating with CdTe have been successfully grown for the first time using the molecular beam epitaxy technique. Four sets of superlattices have been prepared consisting of 14, 60, 90, and 240 double layers of average thickness 460, 140, 75, and 37 A, respectively. Each set consists of two samples grown simultaneously using 7×15×1‐mm thick (0001) sapphire substrates onto which 5.0‐μm‐thick CdTe buffer layers were first deposited. X‐ray diffraction techniques were employed to verify that epitaxy had been achieved and to obtain the average lattice constant of each of the multilayer structures. X‐ray diffraction satellites were observed on both sides of the (111) diffraction peak of the superlattices composed of 14 and 60 alternating layers, respectively, which allowed an accurate estimate of the superlattice period, or double‐layer thickness, for these samples. Results of UV reflectance studies and photoluminescence experi...
TL;DR: In this paper, it was shown that up to 1.5 at.% boron atoms in solution tend to occupy the interstitial sites, generate large lattice strain, and thereby strengthen the Ni3Al substantially.
TL;DR: In this article, the authors used the neutron powder profile refinement technique to determine the crystal structure of solid Br2 at 5, 80, 170 and 250 K and that of solid Cl2 at 22, 55, 100 and 160 K.
Abstract: The neutron powder profile refinement technique has been used to determine the crystal structure of solid Br2 at 5, 80, 170 and 250 K and that of solid Cl2 at 22, 55, 100 and 160 K. The results confirm that the structures of the two halogens are isomorphous, with space group Cmca at all temperatures. For both halogens the lattice parameters a and b increase monotonically with temperature, but the lattice parameter c decreases at the highest temperatures. The data were analysed assuming both isotropic and anisotropic thermal parameters. The intramolecular bond length and its orientation relative to the b-axis show little change with temperature. For Br2 at 5 K the bond length is 2·301(2) A while a = 6·5672(3), b = 4·4678(2), c = 8·6938(4) A. For Cl2 at 22 K the bond length is 1·994(2) A while a = 6·1453(2), b = 4·3954(1), c = 8·1537(2) A, where the errors quoted are those produced by the profile fitting program.
TL;DR: Quarter-plane autoregressive lattice parameter modeling of two-dimensional fields is developed in this article as a natural extension of one-dimensional lattice parametric theory, which has been confirmed by computer simulations.
Abstract: Quarter-plane autoregressive lattice parameter modeling of two-dimensional fields is developed as a natural extension of one-dimensional lattice parameter theory. Starting with a given data field, four prediction error fields are generated. Their linear combination is used to define and calculate 2-D lattice parameter reflection factors for successive lattice parameter model stages. In addition to developing the basic theory, the presentation includes the relationships between the quarter-plane two-dimensional transfer function and the lattice parameters, the lattice parameter synthesis model for generating a two-dimensional field from a random field input, and lattice parameter stability conditions. The theory has been confirmed by computer simulations. The extension of this lattice parameter theory for the asymmetric half-plane case is to be presented in a subsequent paper.
TL;DR: Stoichiometric molybdenum nitride with sodium chloride-type structure has been prepared by reactive sputtering and by ion implantation of nitrogen into molybenum.
Abstract: Stoichiometric molybdenum nitride with sodium chloride-type structure has been prepared by reactive sputtering and by ion implantation of nitrogen into molybdenum. The lattice parameter of this phase is 0.4212 nm. The superconducting transition temperature is only around 3K in contrast to expectations raised by theoretical and empirical predictions.
TL;DR: In this article, the growth of copper, silver and gold on Mo(110) was studied using low energy electron diffraction and Auger electron spectroscopy and the results were compared with previous results for the same metals on W(110).
TL;DR: The band gap of lead-europium-telluride (Pb1-x EuxTe) was determined from room temperature optical absorption measurements and increases as dEg/dx = 3.5 eV for x ≤ 0.044.
Abstract: The band gap of lead-europium-telluride (Pb1-x EuxTe) was determined from room temperature optical absorption measurements and increases as dEg/dx = 3.5 eV for x ≤ 0.044. Eu atoms bond strongly to a PbTe surface during MBE growth and have a small diffusion coefficient (<1 x 10−16 cm /sec at 370°C). The lattice constant of Pb1-x, Eux Te is a nonlinear function of composition, and lattice-matched growth of Pb1-x Eux Sey Te1-y, on PbTe is demonstrated. Preliminary studies of the electrical properties of Pb1-x Eux Te indicate compensation of n-type (Bi) and p-type (Tl) dopants. These results indicate that Pb1-x Eux Sey Te1-y, may be useful for obtaining diode lasers which emit at wavelengths shorter than those available from Pb1-x, Snx Te.
TL;DR: In this paper, the lattice constants of rare earth hafnates were reported and the luminescence of such activators as Eu+3, Tb+3 and Ti+4 in La2Hf2O7 was described.
TL;DR: In this article, self-consistent para and ferromagnetic LMTO energy band results are presented for Fe (bcc structure), Co (hcp and fcc structure) and Ni (fcc structure).
TL;DR: In this paper, the energy of an fcc plane in contact with a bcc substrate was calculated as a function of relative position, orientation, vertical displacement, and ratio of fcc/bcc lattice parameters.
Abstract: We have performed a rigid-lattice, atomistic, model calculation for bcc-fcc epitaxy. We have calculated the energy of an fcc (111) plane in contact with a bcc (110) substrate as a function of relative position, orientation, vertical displacement, and ratio of fcc/bcc lattice parameters. The results show two orientations for which deep minima exist in the dependence of energy on the fcc/bcc lattice parameter ratio. Our results are in qualitative agreement with earlier Moir\'e pattern studies. The calculations were made with two different atom-atom potentials; the results are found to be independent of the long-range attractive part of the potential. This implies that for rigid lattices the energetics is only determined by the relative atomic sizes of the substrate and overlayer. A comparison with experimental results indicates that the growth of metallic superlattices is controlled not only by epitaxial energetics but also by the stacking of the various constituents.
TL;DR: The saturation magnetization and the magnetocrystalline anisotropy were measured on single crystals in the solid solution series SrZn 2-x Co x Fe 16 O 27 (SrZn2-xCo x -W) at 298 K and 6 K Lattice constants and Curie-temperatures are also given as a function of the composition as discussed by the authors.
Abstract: The saturation magnetization and the magnetocrystalline anisotropy were measured on single crystals in the solid solution series SrZn 2-x Co x Fe 16 O 27 (SrZn 2-x Co x -W) at 298 K and 6 K Lattice constants and Curie-temperatures are also given as a function of the composition The magnetocrystalline anisotropy changes from uniaxial to planar dependent on temperature and cobalt substitution at x \approx 05 for 6 K and x \approx 085 for 298 K The six-fold anisotropy in the basal plane of the planar W-hexaferrites increases strongly with increasing cobalt content Crystals with a low Co substitution (x = 033 and 067) have an anomalous discontinuity in their hard direction magnetization curves; indicating a first-order magnetization process
TL;DR: Subsolidus phase relations in the low-Y2O3 portion of the system ZrO2-Y 2O3 were studied using DTA with fired samples and X-ray phase identification and lattice parameter techniques with quenched samples.
Abstract: Subsolidus phase relations in the low-Y2O3 portion of the system ZrO2-Y2O3 were studied using DTA with fired samples and X-ray phase identification and lattice parameter techniques with quenched samples. Approximately 1.5% Y2O3 is soluble in monoclinic ZrO2, a two-phase monoclinic solid solution plus cubic solid solution region exists to ∼7.5% Y2O3 below ∼500°C, and a two-phase tetragonal solid solution plus cubic solid solution exists from ∼1.5 to 7.5% Y2O3 from ∼500° to ∼1600°C. At higher Y2O3 compositions, cubic ZrO2 solid solution occurs.
TL;DR: In this article, the effect of electrostriction on piezoelectric activity has been investigated in a ferroelectric copolymer of vinylidene fluoride and trifluoroethylene with a composition of 52/48 mol%.
Abstract: The effect of electrostriction on piezoelectric activity has been investigated in a ferroelectric copolymer of vinylidene fluoride and trifluoroethylene with a composition of 52/48 mol%. The electrostriction constants determined from changes in lattice spacing and the spontaneous polarization associated with a ferroelectric-to-paraelectric transition induce piezoelectric activities, positive d31 and negative d32. The combined contributions from the dimensional effect and the electrostrictire coupling are consistent with the magnitude and anisotropy of observed piezoelectric constants.
TL;DR: In this paper, large-faceted monocrystals of blue phase I were grown and observed in coexistence with the isotropic liquid, and it was shown that the (200) planes Bragg reflect approximately the same wavelength as the cholesteric spiral.
Abstract: Large-facetted monocrystals of blue phase I are grown and observed in coexistence with the isotropic liquid. Observations of this three-dimensional polyhedral habit, combined with a conjecture that facets perpendicular to screw axes are absent, are compatible with the $I({4}_{1}32)$ space group for blue phase I. The (200) planes Bragg reflect approximately the same wavelength as the cholesteric spiral indicating that the blue phase I lattice constant is the cholesteric pitch even very close to the isotropic phase.
TL;DR: In this paper, the mixing enthalpy of ternary tetrahedral semiconductor alloys is derived from a model which ascribes the mixing entropy to bond distortions associated with the alloy formation, and relates these to the macroscopic elastic properties of the crystal.
Patent•
20 Dec 1984
TL;DR: In this paper, the lattice constant of Si is 5.43Angstrom and that of gallium phosphorus compound was 5.45Angstrom, and the Si layer and GaP layer showed good epitaxial growth with good crystallization characteristic.
Abstract: PURPOSE:To realize good crystallization characteristic, high mobility and high luminescence in the visible region by sequentially stacking a single crystal thin film consisting of Si and that consisting of gallium phosphorus compound at a semiconductor material of the super-lattice structure. CONSTITUTION:The lattice constant of Si is 5.43Angstrom and that of GaP is 5.45Angstrom . Since the lattice constants are approximated, the Si layer and GaP layer show good epitaxial growth with good crystallization characteristic. Moreover, since a band gap of Si is 1.12eV, EG of GaP is 2.24eV, difference of EG between super lattices is large and increment of mobility and that in probability of light emission transition are large. In addition, both Si GaP are indirect transition type semiconductors, but the direct transition type transition probability is generated in the band of both layers by employing the super-lattice structure. Thereby, the material emits the light of infrared region with the wavelength of 1.1mum and the light of visible region with the wavelength of 5,530Angstrom .
TL;DR: In this paper, it was shown that the cubic and the rhombohedral structures of rare earth sulfides coexist, and the structural type of the cubic phase can be regarded as analogous to that of NaCl.