NiAs Structure Research Articles

Octatelluridohexakis(triethylphosphine)hexacobalt and a connection between Chevrel clusters and the NiAs structure

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOctatelluridohexakis(triethylphosphine)hexacobalt and a connection between Chevrel clusters and the NiAs structureM. L. Steigerwald, T. Siegrist, and S. M. StuczynskiCite this: Inorg. Chem. 1991, 30, 10, 2256–2257Publication Date (Print):May 1, 1991Publication History Published online1 May 2002Published inissue 1 May 1991https://doi.org/10.1021/ic00010a005RIGHTS & PERMISSIONSArticle Views377Altmetric-Citations41LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (298 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

The Co-Sb phase diagram and some properties OF NiAs-type Co1 ± xSb

The Co-Sb phase diagram has been investigated between 20 and 85 at.% Sb. The congruent melting point of Co 1 ± x Sb (with NiAs structure) was found at 47.0 ± 0.5 at.% Sb and 1493 ± 5 K. Lattice parameters, pycnometric densities and magnetic susceptibilities of this phase were determined at ambient temperature as a function of composition; they all exhibit a change in slope at the equiatomic composition. These effects are explained by the change in the defect mechanism from a defected NiAs structure on the antimony-rich side of the stoichiometric composition to a partially filled structure on the cobalt-rich side.

Wide-gap II–VI heterostructures

New advances in epitaxial growth techniques have contributed to an improved understanding of the properties of II–VI materials and their alloys. The creation of novel heterojunctions, quantum well structures, and strained-layer superlattices, composed of II–VI/III–V and II–VI/II–VI multilayers, can be attributed to their successful epitaxial growth by molecular beam epitaxy (MBE). The objective of this paper is to discuss some recent advances in the growth of II–VI/III–V and II–VI/II–VI heterostructures, with emphasis on two particular topics. In the first, pseudomorphic epilayer/epilayer heterojunctions consisting of ZnTe on AlSb, a configuration with potential for the development of injection light emitting devices, have been grown by MBE. Microstructural and optical evaluation has indicated a high structural quality. The second topic describes the use of MBE for the growth of novel structures incorporating a previously hypothetical magnetic semiconductor, the zincblende phase of MnTe. Characterization using TEM and X-ray diffraction reveals only the zincblende phases of MnTe. Whereas bulk crystals of MnTe having a NiAs structure with a bandgap of 1.3 eV, the zincblende phase exhibits a bandgap of 3.2 eV. Single quantum well structures incorporating zincblende MnTe exhibit 2D electron and hole confinement in both CdTe and ZnTe quantum wells, and serve to confirm the zincblende MnTe bandgap at 3.2 eV.

Epitaxial growth of MnTe on CdTe(110)

Thin films of MnTe were grown by molecular beam epitaxy on CdTe(l 10). Angle resolved synchrotron radiation photoemission spectroscopy shows that MnTe grows initially in the metastable zinc blende structure In registry with the substrate. After a film thickness of 4̃0 Å the overlayer relaxes Into the thermodynamically stable hexagonal NiAs structure. Above 1̃00 C the MnTe/CdTe heterostructure is thermally unstable. At −250 C the MnTe film reacts with the substrate and forms an epitaxial overlayer of MnCdTe 2. Comparison of the valence band photoemission spectra with calculated density of states suggests the formation of a ferromagnetic ordered MnCdTe 2 compound rather then the thermodynamlcally more favorable phase separation into antiferromagnetic MnTe 2 and zinc-blende CdTe.

Electron-gas theory of some phases of magnesium oxide.

In this paper we investigate the relative stability of the B1 (NaCl), B2 (CsCl), B3 (ZnS), B4 (BeO), and B8 (NiAs) structures for MgO using an ionic bonding model with the short-range repulsions calculated using the modified electron-gas (MEG) model. The short-range pair potentials are generated from anion wave functions which are consistent with the electrostatics of the crystal lattice. We include corrections for the van der Waals energy. Our predictions for the zero-pressure B1 lattice constant and bulk modulus agree with experiment. The MEG ionic model, with van der Waals energy terms included, accounts for all of the experimental lattice energy. The B2 phase becomes stable relative to B1 at pressures above about 600 GPa. The B3 structure is less stable than B4 by about 8 kJ/mole for all calculated volumes. Finally, the hexagonal B8 packing arrangement is never stable relative to B1. In order to understand more fully the high-pressure behavior of oxides, we propose an additional self-consistency criterion for the calculation of the oxide electron density in future theoretical investigations of bonding in minerals. The charge on the Watson sphere used to stabilize the anion wave function should be consistent with the total charge inside the sphere, i.e., the size of the oxide ion. A charge of 1.7 a.u. on a Watson sphere, instead of 2.0, gives denser and more stable zero-pressure B1 and B2 structures. This may have ramifications for the modeling of oxide structures and phase stability at extreme pressures.

Linearized augmented plane wave electronic structure calculations for MgO and CaO

We present full‐potential self‐consistent linearized augmented plane wave (LAPW) calculations for the electronic structure and total energy of MgO and CaO, within the local density approximation. Calculated equilibrium properties are in good agreement with experiment. We also consider the transition from the low‐pressure sodium chloride (B1) structure to the high‐pressure cesium chloride (B2) structure for MgO and CaO and the transition to the NiAs (B8) structures for MgO. In calcium oxide we find that the B1‐B2 transition occurs at 54 GPa, in agreement with the experiment. In magnesium oxide a transition from B1 to B2 is found at 510 GPa. This is a factor of 2 lower than found by a previous pseudopotential calculation. We find no transition to the B8 structure at any pressure. The calculated charge densities of MgO and CaO are very close to the charge densities calculated from the overlap of spherical ions used in the potential induced breathing (PIB) model at zero pressure. More significant deviations from overlapping ions are found at extreme pressures. Near equilibrium, the error in the PIB model (compared to the LAPW calculation) is of the same order as the error in the LAPW calculation (compared to the experiment).

Total-energy and band-structure calculations for the semimagnetic Cd1-xMnxTe semiconductor alloy and its binary constituents.

Spin-polarized, self-consistent local-spin density total-energy and band-structure calculations have been performed for CdTe, antiferromagnetic (AF) MnTe in its NiAs structure, ferromagnetic (F) ${\mathrm{CdMnTe}}_{2}$, and the hypothetical zinc-blende phase of MnTe in the F and AF spin arrangements. We find the following: (i) The alloy environment stabilizes a zinc-blende form of MnTe, hitherto unknown to exist in the phase diagram of pure MnTe. Its calculated Mn---Te bond length (2.70\ifmmode\pm\else\textpm\fi{}0.02 A\r{}) is very close to that observed in the alloy (2.73 A\r{}), but is substantially different from the Mn---Te bond length in pure (NiAs-type) MnTe (2.92 A\r{}). (ii) AF zinc-blende MnTe is more stable than F zinc-blende MnTe due to a reduced p-d repulsion in the upper valence states. (iii) F ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$Te is more stable than its zinc-blende constituents CdTe + F MnTe, hence, once formed, this ordered alloy will not disproportionate. (iv) Nevertheless, AF ${\mathrm{CdMnTe}}_{2}$ is more stable than its ferromagnetic counterpart, but it is unstable relative to its constituents CdTe + AF MnTe. Hence, if F ${\mathrm{CdMnTe}}_{2}$ converts into AF ${\mathrm{CdMnTe}}_{2}$, the latter will disproportionate into antiferromagnetic domains of MnTe. (v) The band structure of F zinc-blende MnTe and F ${\mathrm{CdMnTe}}_{2}$ predicts a novel type of negative (p-d) exchange splitting, whose origins are discussed in terms of a p-d repulsion mechanism. (vi) The calculated electronic states of ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$Te show a vanishing optical bowing, a Mn ${d}_{\ensuremath{\uparrow}}$ band at ${E}_{v}$-2.5 eV and explains the observed optical transitions. (vii) The fact that ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$Te does exhibit localized multiplet transitions but NiAs-type MnTe does not, is explained in terms of the coexistence of covalency and low symmetry in the latter case.We discuss the electronic structures, local magnetic moments, exchange interaction coefficients, and the general features of the chemical bonds in the semimagnetic semiconductor.

REFLECTIVITY AND MAGNETO-OPTICAL SPECTRA IN A SINGLE CRYSTAL OF Fe7Se8

Optical and magneto-optical properties of a single crystal of metallic ferrimagnet Fe7Se8 grown by Bridgmann technique have been measured. This material crystallizes in hexagonal NiAs structure with a superstructure associated with the ordering of vacant Fe sites. Spectra of normal incidence reflectivity and polar magneto-optical Kerr effect were measured at room temperature. From these spectra diagonal and off-diagonal elements of conductivity tensor were evaluated. The results do not clearly show a contribution of intraband transition to the magneto-optical effect, but suggest a contribution of a band-to-band transition starting just below 0.5 eV. This implies the existence of a spin-orbit coupled band with large density of states just below the Fermi-level as supposed from its magnetic properties.

Alloy-stabilized semiconducting and magnetic zinc-blende phase of MnTe.

While MnTe has the stable NiAs structure with a direct band gap of 1.30 eV and a Mn-Te bond length of 2.92 \AA{}, extrapolation of the data for the zinc-blende alloy ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Te}$ to $x=1$ suggests an alloy-stabilized MnTe phase with very different properties: a band gap of \ensuremath{\sim}3 eV and a Mn-Te bond length of 2.73 \AA{}. We model the structural, magnetic, and electronic properties of such a hitherto unknown zinc-blende-like MnTe phase through spin-polarized total-energy calculations, and report its unusual properties in both ferromagnetic and antiferromagnetic spin ordering.

Polytypes of the system Fe1−xS

AbstractThe structures of Fe1−xS (0 < x < 0.135) are members of a family of derivative structures in the sense of Megaw. The NiAs structure as aristotype is the simplest and most symmetrical member of this family. The other polytypes of Fe1−xS may be derived as hettotypes by lowering the symmetry. The loss of symmetry in changing from the aristotype to the hettotype may be of various kinds: small displacements of Fe and S atoms from the NiAs positions and/or Fe vacancies in some atomic planes occur. The structures of the system Fe1−xS are interpreted as OD structures consisting of OD layers. The symmetry relations of the structures of FeS and Fe7S8 are described by OD groupoid families. Polymorphism, twinning and stacking faults are explained on this basis.

The binary systems FeS-MgS and FeS-MnS: Mössbauer spectroscopy of the B1 solid solutions and high-pressure phase equilibria

(Fe, Mn)S and (Fe, Mg)S solid solutions are examined to study and compare the properties of Fe2+ in two different B1-structured hosts, and also to study the relative stability of the B1 (NaCl) and B8 (NiAs) structures at high pressure. The Mossbauer spectra of (Fe, Mn)S and (Fe, Mg)S B1 solid solutions are quadrupole doublets at 298 K with parameters which vary smoothly with Fe2+ concentration. At 4.2 K the Mossbauer spectra of (Fe, Mn)S and Fe-rich (Fe, Mg)S B1 solid solutions are magnetically split into eight lines, but the spectra of Mg-rich (Fe, Mg)S solid solutions are quadrupole doublets. The line widths of the magnetic spectra are broad, consistent with a multiaxial spin arrangement. Some properties of the hypothetical phase FeS(B1) are calculated from the solid solution data; the phase is inferred to be relatively ionic compared to FeS(B8) and has a molar volume that is 7.2 percent larger than the B8 phase at 298 K. The large inferred volume difference between FeS(B1) and FeS(B8) should cause exsolution of a B8-structured phase from (Fe, Mn)S and (Fe, Mg)S B1 solid solutions at high pressure. This behaviour is confirmed experimentally at high pressure using X-ray diffraction and Mossbauer spectroscopy, and the results are correlated with thermodynamic calculations of the phase boundaries based on estimates of the volume and free energy differences between the B1 and B8 phases of FeS derived from atmospheric pressure data. The absence of an increase in solubility of Mg and Mn in the B8 phase with pressure suggests that any polymorphism in MnS and MgS at high pressure is unlikely to involve the B8 phase. Shock wave data for MgO and Fe0.94O reported in the literature suggest similar behaviour in the system FeO-MgO at high pressure, namely exsolution of essentially pure FeO(hpp) from (Fe, Mg)O B1 solid solutions.

Influence of nickel substitution in an Fe-Sb triangular antiferromagnetic system

The iron-antimony system, which occurs in a Ni-As structure, shows interesting magnetic properties and has been investigated by several workers. In order to explore these properties further, we have studied ${({\mathrm{Fe}}_{1\ensuremath{-}y}{\mathrm{Ni}}_{y})}_{1+x}\mathrm{Sb}$ by x-ray diffraction and M\"ossbauer methods in the concentration ranges $0.02\ensuremath{\le}y\ensuremath{\le}0.42$ and $0.08\ensuremath{\le}x\ensuremath{\le}0.16$. Through analysis of the x-ray data, it has been found that these samples are isotypic with ${\mathrm{Fe}}_{1+x}\mathrm{Sb}$, wherein Fe is substituted by Ni, and that the American Society for Testing and Materials data file for ${\mathrm{Fe}}_{1+x}\mathrm{Sb}$ needs modification. Using M\"ossbauer spectroscopic measurements in a transmission geometry at different temperatures, we have determined the N\'eel temperatures, which decrease linearly with increasing $y$. The substitution of Ni atoms in the Fe-Sb lattice produces two new magnetic hyperfine fields which are about 40% and 80% lower than the original field in Fe-Sb. The magnitude of these fields is independent of Ni concentration, whereas the density of sites with these fields increases monotonically with the increase in $y$.

The site distribution of Ti and V and the metal-metal interaction in the ternary system (V,Ti) 5S 8

The phase relations of the ternary system V 1− x Ti x S 1.57 are presented on the basis of X-ray diffractometry. The site distribution of Ti and V atoms in the structure is clarified through an NMR absorption study at room temperature. The phase relations and the site distribution of Ti and V, which appear to be closely related to each other, are discussed in terms of the metal-metal interaction of the face-shared octahedra in the metal-deficient distorted NiAs structure.

Transmission electron microscopy on meteoritic troilite

Phase transitions and associated domains of meteoritic troilite (FeS) have been studied by means of transmission electron microscopy (TEM). Three polymorphs have been found, two of which can be described by superstructures of the NiAs-type structure (A, C subcell). The P\(\overline 6\)2c (√3A, 2C) polymorph, stable at room temperature, displays antiphase domains with the displacement vector 1/3 . In situ heating experiments showed that the P\(\overline 6\)2c polymorph changes at temperatures of 115°–150° C into an orthorhombic pseudohexagonal transitional phase with the probable space group Pmcn (A,√3A, C). It contains antiphase domains with the displacement vector 1/2 [110] and twins with a threefold twin-axis parallel c. When heated above 210° C the transitional phase transforms into the high-temperature modification with NiAs structure (P63/mmc). All observed phase transitions are reversible. The occurrence of antiphase and twin domains, respectively, agrees with the symmetry reductions involved in the subsolidus phase transitions. This is demonstrated by group-subgroup relationships among the space groups P63/mmc, Pmcn, and P\(\overline 6\)2c.

Cesium chloride versus nickel arsenide as possible structures for (Mg, Fe)O in the lower mantle

Thermochemical systematics are used to estimate the pressure for the transition from rocksalt to cesium chloride and from rocksalt to nickel arsenide structures. For MgO, both transitions are predicted to occur at pressures greater than 3000 kbar, which implies that neither transition is likely for MgO in the lower mantle. For FeO, the transition to nickel arsenide is predicted to occur at much lower pressure (∼300 kbar) than that to cesium chloride (3000 kbar), and it is suggested that the transition observed by Jeanloz and Ahrens in shock experiments near 700 kbar may be to the nickel arsenide structure. If a (Mg, Fe) O solid solution with NiAs structure exists in the lower mantle as a minor phase, it will be strongly enriched in iron and other transition metals relative to a (Mg, Fe) SiO3 perovskite phase. This enrichment in the heavier elements, as well as the slightly higher density of nickel arsenide than rocksalt phases, would accentuate the density difference between MSiO3 and MO phases and enhance gravitational settling and lower mantle heterogeneity.

Solid state reactions in chalcogenide systems. VI. Ion distribution equilibria between MCr 2(S, Se) 4 spinel solid solutions and M(S, Se) or Cr 2(S, Se) 3 solid solutions

The sulfur/selenium exchange equilibria between spinel solid solutions MCr 2(S, Se) 4 ( M = Zn and Cd) and M(S, Se) or Cr 2(S, Se) 3 solid solutions with sphalerite, wurtzite, and defect NiAs structure have been determined by X-ray diffraction measurements of reaction mixtures quenched from 1073 and 1273 K, respectively. With the exception of the CdCr 2X 4 Cr 2X 3 system, there is a clear preference for incorporation of sulfur in the spinel structure, increasing in the series ZnCr 2X 4 Cr 2X 3 < ZnCr 2X 4 ZnX < CdCr 2X 4 CdX . Both equilibrium constants and reaction heats, including data on M Cr 2S 4 M′ S (M, M′ = Mn, Co, Zn, and Cd) metal ion distribution equilibria, are given. Revised X-ray data on the solid solutions are also presented.

De Haas-van Alphen effect and Fermi surface of PdSb and other NiAs structure compounds

High-field de Haas-van Alphen measurements in PdSb are reported and a semi-quantitative comparison is made with a recent bandstructure calculation. The interpretation of the de Haas-van Alphen branches is given extra support by a Fourier series description of some of the sheets. On the whole the Fermi surface is rather free-electron like despite the presence of the Pd d-bands near the Fermi energy. A comparison with the Fermi surfaces of AuSn and PtSn is made, from which the general features are expected to hold for all NiAs-structure compounds which are isoelectronic with either PdSb or PtSn.

Spin Glass State of MnxNi1-xSb: Synthesis in High Pressure and High Temperature Atmospheres

The solid solution between ferromagnetic MnSb and paramagnetic NiSb, Mn x Ni 1- x Sb (0≤ x ≤1.0), with NiAs structure was synthesized in high pressure and high temperature atmospheres. The decomposition temperature was determined to be 420∼480 K. The critical concentration of ferromagnetism was obtained to be x c =0.65 at absolute zero. A new type spin glass state with double transition points, T sg1 and T sg2 , was found in a wide range of 0.2≤ x ≤0.65 in the paramagnetic phase. The maximum transition point was estimated to be T sg1 =60 K and T sg2 =190 K. The electrical resistivity showed no anomaly corresponding to T sg1 and T sg2 , and the temperature dependence in the spin glass state was given to be T 2 and T 3/2 at lower temperature. Some discussions are given for the experimental results.

Physicochemical properties and crystal growth of A IIB VI - MnB VI systems

Work on the solid solutions of Mn chalcogenides in II–VI compounds is collected together and summarized. It is found that the manganese compounds show extensive solubility in the II–VI compounds when the anion is common exhibiting adamantine structures. Only cadmium chalcogenides show a little solubility in MnBVI compounds. Cadmium (S, Se) and (Te) exhibit the rock salt and Nias structure MnVI compounds, respectively. The crystal growth of the various alloys is discussed and tables of physicochemical properties and growth conditions are given.

Kristallstruktur von Pt 1+In

The phase Pt 1+In crystallizes in the CuAl. r type. The relation of this type to the NiAs structure is discussed. The two-correlations model affords a low energy binding for all phases of the mixture Pt-In.