Showing papers on "Lattice constant published in 1986"
TL;DR: A consistent set of embedding functions and pair interactions for use with the embedded-atom method was determined empirically by fitting to the sublimation energy, equilibrium lattice constant, elastic constants, and vacancy-formation energies of the pure metals and the heats of solution of the binary alloys as discussed by the authors.
Abstract: A consistent set of embedding functions and pair interactions for use with the embedded-atom method [M.S. Daw and M. I. Baskes, Phys. Rev. B 29, 6443 (1984)] have been determined empirically to describe the fcc metals Cu, Ag, Au, Ni, Pd, and Pt as well as alloys containing these metals. The functions are determined empirically by fitting to the sublimation energy, equilibrium lattice constant, elastic constants, and vacancy-formation energies of the pure metals and the heats of solution of the binary alloys. The validity of the functions is tested by computing a wide range of properties: the formation volume and migration energy of vacancies, the formation energy, formation volume, and migration energy of divacancies and self-interstitials, the surface energy and geometries of the low-index surfaces of the pure metals, and the segregation energy of substitutional impurities to (100) surfaces.
3,734 citations
PARC1
TL;DR: A theoretical study of the structural and electronic properties of pseudomorphic Si/Ge interfaces, in which the layers are strained such that the lattice spacing parallel to the interface is equal on both sides.
Abstract: We present a theoretical study of the structural and electronic properties of pseudomorphic Si/Ge interfaces, in which the layers are strained such that the lattice spacing parallel to the interface is equal on both sides. The self-consistent calculations, based on the local density functional and ab initio pseudopotentials, determine the atomic structures and strains of minimum energy, and the lineup of the Si and Ge band structures. The presence of the strains causes significant shifts and splittings of the bulk bands. We derive values for the band discontinuities for (001), (111), and (110) interfaces under different strain conditions, and discuss the validity of the density-functional methods for the analysis of the interface problem. Spin-orbit splitting effects in the valence bands are included a posteriori. We express our results in terms of discontinuities in the valence bands, and deformation potentials for the bulk bands, and compare them with recent experiments on Si/${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ge}}_{\mathrm{x}}$ heterostructures.
1,108 citations
TL;DR: In this paper, lattice parameter and density data were compiled for Y2O3-Stabilized ZrO2, both from the literature and from experimental measurements, and the data were described very well over a wide range of composition by the model of Aleksandrov et al., which assumes Y substitution for Zr in the unit cell with compensating anion vacancies.
Abstract: Lattice parameter and density data were compiled for Y2O3-Stabilized ZrO2, both from the literature and from experimental measurements. The data are described very well over a wide range of composition by the model of Aleksandrov et al., which assumes Y substitution for Zr in the unit cell with compensating anion vacancies. Effects are noted in two-phase cubic-tetragonal materials which indicate significant lattice strains in the two-phase materials.
338 citations
TL;DR: A pseudopotential study within the local-density formalism of the structural and electronic properties of zinc-blende BN and BP finds that the valence charge density of BP shows two local maxima along the bond, which is similar to the case of diamond.
Abstract: We present a pseudopotential study within the local-density formalism of the structural and electronic properties of zinc-blende BN and BP. The ground-state properties of these systems such as bulk moduli, lattice constants, cohesive energies, and frequencies of the TO phonon mode are in good agreement with experimental results. The valence charge density of BP shows two local maxima along the bond, which is similar to the case of diamond. In contrast, the charge density of BN is similar to that of a typical III-V compound semiconductor. The resulting band structures have some important features which are in disagreement with previously published work. Like most III-V compound semiconductors, the fundamental gap in BP decreases with decreasing volume. The corresponding gap in BN, however, increases with decreasing volume as was also found in diamond.
227 citations
TL;DR: In this paper, a quantum mechanical lattice model of fermionic electrons interacting with infinitely massive nuclei is considered and it is shown that for all dimensions, d, the ground state has long range order.
Abstract: A quantum mechanical lattice model of fermionic electrons interacting with infinitely massive nuclei is considered. (It can be viewed as a modified Hubbard model in which the spin-up electrons are not allowed to hop.) The electron-nucleus potential is “on-site” only. Neither this potential alone nor the kinetic energy alone can produce long range order. Thus, if long range order exists in this model it must come from an exchange mechanism. N , the electron plus nucleus number, is taken to be less than or equal to the number of lattice sites. We prove the following: (i) For all dimensions, d, the ground state has long range order; in fact it is a perfect crystal with spacing √2 times the lattice spacing. A gap in the ground state energy always exists at the half-filled band point ( N = number of lattice sites). (ii) For small, positive temperature, T, the ordering persists when d ⩾ 2. If T is large there is no long range order and there is exponential clustering of all correlation functions.
215 citations
TL;DR: In this article, the phase diagram Nb2O5-Li2O-MgO was investigated and a single phase area up to 15 mol% MgO were found.
165 citations
TL;DR: In this article, two groups of reactively sputtered TiN films, gold-yellow films (G films) with low resistivity and high compressive internal stress and brown-black films (B films), which are formed with and without a negative substrate bias, were examined as potential diffusion barriers.
157 citations
TL;DR: In this article, the photoluminescence (PL) linewidths at 2 K were the narrowest that have been ever reported for Ga0.47In0.53As quantum wells grown by any technique.
Abstract: We have prepared by chemical beam epitaxy extremely high quality Ga0.47In0.53As/InP quantum wells with thickness as thin as 6 A. Emission as short as 1.09 μm at 2 K (1.14 μm at 300 K) was obtained. Very sharp intense efficient luminescence peaks due to excitonic transitions were obtained from all quantum wells. The photoluminescence (PL) linewidths at 2 K were the narrowest that have been ever reported for Ga0.47In0.53As quantum wells grown by any technique. In fact, these Ga0.47In0.53As quantum well linewidths are at least equal to the narrowest linewidths ever reported for the perfected GaAs/AlAs and GaAs/AlxGa1−xAs quantum wells. These linewidths indicate the ‘‘effective’’ interface roughness to be 0.12 lattice constant, which can be interpreted as that the quantum well was largely consisting of a big domain of the same thickness Lz perforated with a small fraction of small domains of (Lz+a0/2), where a0 (=5.86 A) is the lattice constant. No broadening due to band filling from impurities was found. All...
148 citations
TL;DR: Rietveld analyses of room-temperature neutron diffraction data for seven Nd2(Co/x/Fe/1-x/)14B alloys (x = 0,0.1, 0.3, 0.,5, 0,7, 0.9, 1) are reported in this paper.
Abstract: Rietveld analyses of room-temperature neutron diffraction data for seven Nd2(Co/x/Fe/1-x/)14B alloys (x = 0,0.1, 0.3, 0.5, 0.7, 0.9, 1) are reported. Throughout the entire composition range the Nd2Fe14B-type tetragonal crystal structure is maintained, with the lattice constants decreasing significantly as the Co concentration x increases. It is found that the J2-type transition-metal sites are preferentially occupied by Fe ions in the pseudoternary systems, a result which is analogous to the preferential Fe occupation of c sites previously observed in hexagonal Nd2(Co/x/Fe/1-x/)17 alloys.
130 citations
01 Jan 1986
TL;DR: In this article, the density of solids and the lattice constants (for the latter see “Uranium” Suppl. Vol. C4, 1984, pp. 112/7) are directly interrelated.
Abstract: The density of solids and the lattice constants (for the latter see “Uranium” Suppl. Vol. C4, 1984, pp. 112/7) are directly interrelated. In general the X-ray density calculated from the lattice constants agrees very well with the density determined from pycnometric measurements. Except for a relatively narrow temperature range in the neighborhood of the melting point, the dilatometrically measured thermal expansion coefficient generally agrees well with the lattice constant changes determined via X-ray diffraction. In uranium dioxide, however, several additional difficulties arise, which make the measurements uncertain and the results less comparable.
119 citations
TL;DR: In this article, the principal axial coefficients of thermal expansion of hexagonal alpha SiC have been determined by X-ray diffraction measurements in the temperature range 20-1000 C. Alpha(11) was found to be larger than alpha(33) over the entire temperature range.
Abstract: The principal axial coefficients of thermal expansion, alpha(11) and alpha(33), of the (4H) polytype of hexagonal alpha SiC have been determined by X-ray diffraction measurements in the temperature range 20-1000 C. Alpha(11) and alpha(33), derived from the lattice parameter measurements, were expressed as the second-order polynomials in temperature. Alpha(11) was found to be larger than alpha(33) over the entire temperature range, with a thermal expansion anisotropy factor A increasing from 0.04 at room temperature to 0.11 at 1000 C. The thermal expansion results for the (4H) structure were compared with previously published results for the cubic (3C) and the hexagonal (6H) SiC polytypes.
TL;DR: In this article, the first solid state reaction of their binary components 2H-CuScO2, R-CuGaO2 and R-cuYO2 were synthesized for the first time.
Abstract: Durch Feststoffumsetzung aus den binaren Komponenten wurden 2H-CuScO2, R-CuGaO2 und R-CuYO2 erstmals dargestellt und ihre Kristallstrukturen bestimmt sowie diejenigen von R-CuAlO2 und 2H-CuAlO2 verfeinert. Charakteristische Strukturparameter (Gitterkonstanten und Bindungsabstande) werden im Hinblick auf mogliche Cu+Cu+-Wechselwirkungen diskutiert.
Synthesis and Structural Data of “Delafossites” CuMO2 (M = Al, Ga, Sc, Y)
By solid state reaction of their binary components 2H-CuScO2, R-CuGaO2, and R-CuYO2 were synthesized for the first time. Their crystal structures were determined, and those of R-CuAlO2 and 2H-CuAlO2 refined. Characteristic structural features (lattice constants and interatomic distances) are discussed with respect to possible Cu+Cu+ interactions.
TL;DR: In this paper, a theory of epitaxial growth appropriate to overlayer materials that can adopt a bulk metastable crystal structure with a lattice constant significantly different from that of the stable ground state structure was presented.
Abstract: We present a theory of epitaxial growth appropriate to overlayer materials that can adopt a bulk metastable crystal structure with a lattice constant significantly different from that of the stable ground state structure, as is common for metal epitaxy. This requires a generalization of the traditional Frank and van der Merwe theory to a regime where the overlayer responds nonlinearly to the large shear stress exerted by the substrate. New results are obtained for the commensurate-incommensurate transition (for thin layers) and the coherent-incoherent transition (for thick layers) that are presented in the form of a structural phase diagram as a function of epitaxial misfit and overlayer thickness. We predict that a crystallographic analog to spinodal decomposition can occur in certain ranges of large misfit. The nature of substrate-stabilized metastable epitaxy is clarified and a further analogy to martensitic phase transitions is exploided to predict the microstructure that must accompany the transformation of a metastable overlayer to the ground state structure for sufficiently thick overlayers Presentation d'une theorie de la croissance epitaxiale adaptee aux materiaux de surcouche pouvant adopter une structure cristallographique metastable volumique avec un parametre cristallin assez different de celui de la structure stable de l'etat fondamental
TL;DR: In this paper, the lattice distortions that occur in the nitride coatings were resolved in terms of a macrostrain and microstrain, as determined from the breadth of the x-ray reflections, and the origins of each are discussed.
Abstract: Titanium nitride coatings were deposited on various substrates by sputter ion plating and the state of stress was determined by the sin2 ψ method. The lattice distortions that occur in the nitride coatings have been resolved in terms of a macrostrain and microstrain, as determined from the breadth of the x‐ray reflections, and the origins of each are discussed. The internal stress present in a coating is shown to consist of two components, one thermal in origin and the other structural, and that its sign and magnitude varies with substrate material and bias potential. During cooling from deposition temperature partial relaxation of this internal stress (macrostrain) occurs via two mechanisms, plastic deformation of the substrate and yield of the film. The internal stress was completely relaxed on dissolution of the substrate, accompanied by a decrease in the lattice parameter of the film. By comparing the results from substrates biased and unbiased during deposition, and measurements made on adherent and free‐standing coatings, the microstrain measurements have been separated into two parts, one due to distortions at the grain boundaries and one due to defects in the crystallites. A model is proposed that accounts for all the experimental observations; this also provides an explanation for the distortions from cubic symmetry reported in titanium and hafnium nitride films.
TL;DR: In this paper, the results of a transmission electron microscopy investigation of the Ni/GaAs reaction are presented, and the first reaction product is shown to have the composition Ni3GaAs.
Abstract: Advanced compound semiconductor devices require increasingly stable, shallow, and uniform metallized layers for ohmic and Schottky contacts. However, the design of new multielemental contact metallization systems is limited by the paucity of information regarding the structure, composition, and stability of phases resulting from the interaction of single metal layers with compound semiconductors. In this letter, the results of a transmission electron microscopy investigation of the Ni/GaAs reaction are presented. The first reaction product is shown to have the composition Ni3GaAs. Based on this composition and lattice parameter measurements, it is proposed that the structure of Ni3GaAs is closely related to that of γ’ Ni3Ga2, a derivative of the hexagonal B8 structure type.
TL;DR: In this paper, the formation of the Fe/GaAs(001)-c(8\ifmmode\times\else\texttimes\fi{}2) interface was examined using high-energy-resolution x-ray photoelectron spectroscopy.
Abstract: We have combined high-angular-resolution Auger-electron diffraction, kinematical scattering calculations, low-energy-electron diffraction (done in a pulse-counting mode), and high-energy-resolution x-ray photoelectron spectroscopy to examine the formation of the Fe/GaAs(001)-c(8\ifmmode\times\else\texttimes\fi{}2) interface. We find that clusters of bcc Fe at least three atomic layers deep grow in registry with the substrate for coverages up to \ensuremath{\sim}4 monolayer equivalents. These clusters contain Ga and As atoms which have been liberated from the GaAs substrate. Above this coverage, the clusters coalesce into a continuous bcc Fe matrix with a lattice constant equal to half that of GaAs and with principal crystallographic axes parallel to those of the substrate. This epitaxial Fe overlayer contains Ga and As in solution in the bcc lattice with the impurity atoms occupying interstitial face-center sites. The concentration of Ga and As decreases with distance from the GaAs substrate. At the same time, we find clear evidence for surface segregation of As and enrichment of the near-surface region.
TL;DR: In this article, a new molecular superconductor based on BEDT-TTF molecule was prepared electrochemically by using the mixed supporting electrolyte, (n-C4H9)4NI3 and (n − C4H8)4NAuI2.
Abstract: A new molecular superconductor based on BEDT-TTF molecule was prepared electrochemically by using the mixed supporting electrolyte, (n-C4H9)4NI3 and (n-C4H8)4NAuI2. The superconducting transition takes place at ambient pressure at 3.6 K. X-Ray diffraction patterns show that the system can be approximately assigned to a pseudo orthorhombic one with the lattice constants of a=10.076(2), b=33.853(5), c=4.964(1) A.
TL;DR: In this article, the electrical conductivity of sintered specimens of (CeO 2 ) 1− x (CaO) x was investigated by employing a standard four-probe dc technique as a function of temperature between 400°C and 900°C, composition from 0.10⩽ x ⩽0.80, and oxygen partial pressure from 10 −18 to 1 atm.
TL;DR: The self-consistent electronic structure of AlN has been calculated using a first-principles linear-combination-of-atomic-orbitals method and is in good agreement with results from x-ray diffraction experiments which indicate the lack of a distinct bond charge.
Abstract: The self-consistent electronic structure of AlN has been calculated using a first-principles linear-combination-of-atomic-orbitals method. Theoretical values for the lattice constant, internal parameter, bulk modulus, and cohesive energy were determined as well as the pressure-dependent frequency of the A/sub 1/ TO phonon. The charge density has also been calculated and is in good agreement with results from x-ray diffraction experiments which indicate the lack of a distinct bond charge.
TL;DR: A large number of intermetallic compounds in which Fe is combined with transition metals (Ti, Zr, Hf, Th, V, Nb, Ta, Mo) and s,p metals or metalloids (B, Al, Ga, Si, Ge, Sn, As, Sb) were investigated by means of X-ray diffraction and 57Fe Mossbauer spectroscopy.
Abstract: A large number of intermetallic compounds in which Fe is combined with transition metals (Ti, Zr, Hf, Th, V, Nb, Ta, Mo) and s,p metals or metalloids (B, Al, Ga, Si, Ge, Sn, As, Sb) were investigated by means of X-ray diffraction and 57Fe Mossbauer spectroscopy. The lattice constants of all compounds were determined. The isomer shift in all these materials was analysed in terms of the model of Miedema and Van der Woude by the same empirical method used earlier in investigations on amorphous Fe-base alloys.
TL;DR: In this article, the pseudopotential method within the local density approximation is used to investigate the structural and electronic properties of the most covalent of the III-V semiconductors, BAs.
Abstract: The pseudopotential method within the local density approximation is used to investigate the structural and electronic properties of the most covalent of the III-V semiconductors, BAs. Results are given for the bulk modulus, lattice constant, cohesive energy and frequency of the TO phonon mode at Gamma . The electronic band structure and charge density are also discussed and shown to have features that differ from those of the other III-V compounds. In particular there is evidence for a reversal of the usual charge transfer between cation and anion.
TL;DR: In this article, the pseudopotential method within the local density approximation was used to investigate the static and structural properties of NaCl and KCl and calculated the electronic energy levels at symmetry points in the Brillouin zone as a function of volume.
Abstract: The pseudopotential method within the local-density approximation is used to investigate the static and structural properties of NaCl and KCl. Calculated values for the lattice constants and bulk moduli are in good agreement with experiment. The pressure phase transformation to the CsCl structure is studied, and the role of the C44 shear instability as a possible transformation path is investigated and dismissed. The tetragonal distortion of the CsCl phase, which has been found in other alkali halides at high pressures, appears not to exist in KCl. Finally the authors have calculated the electronic energy levels at symmetry points in the Brillouin zone as a function of volume.
TL;DR: In this article, anisotropic thermal expansion coefficients based on lattice parameter determinations at room temperature and 600° and 800°C are presented for tetragonal zirconia containing 2 and 3 mol% Y2O3.
Abstract: The transformability of the grains in tetragonal zirconia polycrystals is determined by thermal stresses (eigenstresses) which develop because of anisotropic expansion behavior of the tetragonal grains on cooling. Anisotropic thermal expansion coefficients based on lattice parameter determinations at room temperature and 600° and 800°C are presented for tetragonal zirconia containing 2 and 3 mol% Y2O3. The sources of errors in these data are discussed.
TL;DR: In this article, the epitaxial layers of alloys are grown on sapphire (0001) and silicon (111) substrates by MOVPE in an ambient gas at atmospheric pressure.
Abstract: Epitaxial layers of alloys are grown on sapphire (0001) and silicon (111) substrates by MOVPE in an ambient gas at atmospheric pressure. By optimizing the reactor design and the growth conditions, parasitic reactions of metalorganic compounds with gaseous are remarkably reduced and the composition of layers can be controlled fairly well for the first time. The vapor‐solid distribution coefficient for Al is found to be approximately unity. At respective substrate temperatures of 1020°C for sapphire and 1050°C for silicon, single‐crystal layers of withx up to 0.40 are obtained. The lattice constant is proportional to the molar fraction of following Vegard's law. The electrical resistivity, carrier concentration, and Hall mobility of the layers are studied as a function of the composition.
TL;DR: In this paper, LiNbO3 single crystals were measured using the x-ray rocking curve method and phase modulation technique to examine the relationship between the refractive index and the strain, and the degradation of the electro-optic effect.
Abstract: Lattice constants and electro‐optic constants have been measured on proton‐exchanged LiNbO3 single crystals by means of the x‐ray rocking curve method and the phase modulation technique to examine the relationship between the refractive index and the strain, and the degradation of the electro‐optic effect.
TL;DR: A class of new organic conducting salts α'−(BEDT-TTF)2X with X− = Ag(CN)2−, Au(CN), 2− and AuBr2− were synthesized, and their structures determined by single crystal x-ray diffraction.
TL;DR: The structural properties of lithium, sodium, and potassium are studied with use of an ab initio pseudopotential method to calculate the total energies of these systems as a function of volume and show very small energy differences between the bcc, fcc, and hcp phases in these materials.
Abstract: The structural properties of lithium, sodium, and potassium are studied with use of an ab initio pseudopotential method to calculate the total energies of these systems as a function of volume. The results show very small energy differences between the bcc, fcc, and hcp phases in these materials in good agreement with the measured crystal structures for all three metals. The lattice constants are computed to within 2% of experiment except for sodium where the calculation gives a lattice constant 3% smaller than experiment.
TL;DR: In this paper, a study of the isothermal sections of the Nd-Fe-B phase diagram at 900 °C and 700 °C was performed and it was found that the phase Nd2Fe14B has no or at best only a small homogeneity range.
Abstract: From a study of the isothermal sections of the Nd-Fe-B phase diagram at 900 °C (neodymium-poor alloys) and 700 °C (neodymium-rich alloys) it was found that the phase Nd2Fe14B has no or at best only a very small homogeneity range. Results of a preliminary structure determination are given for Nd2FeB3. Magnetic properties and lattice constants were determined for the compounds NdFe4B4 and Nd2FeB3 and their gadolinium counterparts.
TL;DR: In this article, the magnetic and crystallographic properties of intermetallic compounds of the type Ni1-xFexMnSb were determined using standard X-ray diffraction techniques, magnetic measurements and 57Fe Mossbauer spectroscopy.
TL;DR: In this article, a GaAs grown on Si substrates oriented 2° off (100) with intermediate layers of GaP, GaP/GaAs05P05/GaA superlattice, and GaAs05p05/GAAs super-lattices is characterized for different thickness of GaAs and different directions of the off angle of the Si substrate.