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Title: The incommensurately modulated NiGe{sub 1-x}P{sub x}, {approx}0.3=<x=<{approx}0.7, solid solution: The 'missing link' between the NiP and MnP structure types

Abstract

The (3+1)-d incommensurately modulated structures of four members of the NiGe{sub 1-x}P{sub x} solid solution field have been successfully refined from X-ray powder diffraction data (R{sub w}(all)/R{sub wp}=2.13/3.92; 1.52/4.25; 1.27/3.44 and 2.00/4.03 for x=0.4, 0.5, 0.6 and 0.7, respectively). The 4-d superspace group symmetry is Amam(00{gamma})s00 (Z=4; a=5.0468(2), 5.0188(2), 4.9796(2) and 4.9651(1)A; b=6.0636(3), 6.0576(2), 6.0183(2) and 6.0031(1)A; c=3.4877(2), 3.4812(2), 3.4593(1) and 3.45442(7)A; {gamma}=0.7769(2), 0.7467(1), 0.7241(1) and 0.7046(1) for x=0.4, 0.5, 0.6 and 0.7, respectively). The underlying average structure is of NiAs type while the (in general) incommensurate primary modulation wave-vector, {gamma}c{sup *}, varies continuously and smoothly with composition. The two largest amplitude displacive atomic modulation functions (AMFs), for all samples, were the Ni displacement along b AMF and the Ge/P displacement along a AMF. The refined amplitude of the former was found to systematically increase with P content from 0.215A for NiGe{sub 0.6}P{sub 0.4} to 0.294A for NiGe{sub 0.3}P{sub 0.7} while the magnitude of the latter was found to increase with P content from 0.177A for NiGe{sub 0.6}P{sub 0.4} to 0.253A for NiGe{sub 0.3}P{sub 0.7}. These displacive shifts significantly modulate the local crystal chemistry i.e. the local interatomic distances and co-ordination polyhedra. This continuously variable, incommensurately modulated, intermediate structure typemore » is shown to provide a natural link or bridge between the two extreme end-member structures i.e. NiGe (of MnP structure type) and NiP by simply choosing the commensurate options with {gamma}=1 and 12 respectively.« less

Authors:
 [1];  [2];  [3]
  1. Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia), E-mail: ankie.larsson@anu.edu.au
  2. Lehrstuhl fuer Festkoerperchemie, Instituet for Physik, Universitaet Augsburg, Universitaetsstrasse 1, D-86159 Augsburg (Germany)
  3. Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia)
Publication Date:
OSTI Identifier:
21015751
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 180; Journal Issue: 3; Other Information: DOI: 10.1016/j.jssc.2007.01.006; PII: S0022-4596(07)00023-0; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; GERMANIDES; INTERATOMIC DISTANCES; INTERMEDIATE STRUCTURE; NICKEL PHOSPHIDES; SOLID SOLUTIONS; SYMMETRY; X-RAY DIFFRACTION

Citation Formats

Larsson, A.-K., Garcia-Garcia, F.J., and Withers, R.L.. The incommensurately modulated NiGe{sub 1-x}P{sub x}, {approx}0.3=<x=<{approx}0.7, solid solution: The 'missing link' between the NiP and MnP structure types. United States: N. p., 2007. Web. doi:10.1016/j.jssc.2007.01.006.
Larsson, A.-K., Garcia-Garcia, F.J., & Withers, R.L.. The incommensurately modulated NiGe{sub 1-x}P{sub x}, {approx}0.3=<x=<{approx}0.7, solid solution: The 'missing link' between the NiP and MnP structure types. United States. doi:10.1016/j.jssc.2007.01.006.
Larsson, A.-K., Garcia-Garcia, F.J., and Withers, R.L.. Thu . "The incommensurately modulated NiGe{sub 1-x}P{sub x}, {approx}0.3=<x=<{approx}0.7, solid solution: The 'missing link' between the NiP and MnP structure types". United States. doi:10.1016/j.jssc.2007.01.006.
@article{osti_21015751,
title = {The incommensurately modulated NiGe{sub 1-x}P{sub x}, {approx}0.3=<x=<{approx}0.7, solid solution: The 'missing link' between the NiP and MnP structure types},
author = {Larsson, A.-K. and Garcia-Garcia, F.J. and Withers, R.L.},
abstractNote = {The (3+1)-d incommensurately modulated structures of four members of the NiGe{sub 1-x}P{sub x} solid solution field have been successfully refined from X-ray powder diffraction data (R{sub w}(all)/R{sub wp}=2.13/3.92; 1.52/4.25; 1.27/3.44 and 2.00/4.03 for x=0.4, 0.5, 0.6 and 0.7, respectively). The 4-d superspace group symmetry is Amam(00{gamma})s00 (Z=4; a=5.0468(2), 5.0188(2), 4.9796(2) and 4.9651(1)A; b=6.0636(3), 6.0576(2), 6.0183(2) and 6.0031(1)A; c=3.4877(2), 3.4812(2), 3.4593(1) and 3.45442(7)A; {gamma}=0.7769(2), 0.7467(1), 0.7241(1) and 0.7046(1) for x=0.4, 0.5, 0.6 and 0.7, respectively). The underlying average structure is of NiAs type while the (in general) incommensurate primary modulation wave-vector, {gamma}c{sup *}, varies continuously and smoothly with composition. The two largest amplitude displacive atomic modulation functions (AMFs), for all samples, were the Ni displacement along b AMF and the Ge/P displacement along a AMF. The refined amplitude of the former was found to systematically increase with P content from 0.215A for NiGe{sub 0.6}P{sub 0.4} to 0.294A for NiGe{sub 0.3}P{sub 0.7} while the magnitude of the latter was found to increase with P content from 0.177A for NiGe{sub 0.6}P{sub 0.4} to 0.253A for NiGe{sub 0.3}P{sub 0.7}. These displacive shifts significantly modulate the local crystal chemistry i.e. the local interatomic distances and co-ordination polyhedra. This continuously variable, incommensurately modulated, intermediate structure type is shown to provide a natural link or bridge between the two extreme end-member structures i.e. NiGe (of MnP structure type) and NiP by simply choosing the commensurate options with {gamma}=1 and 12 respectively.},
doi = {10.1016/j.jssc.2007.01.006},
journal = {Journal of Solid State Chemistry},
number = 3,
volume = 180,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • The structure, the energetics and the internal redox reactions of La{sub 0.7}Sr{sub 0.3}Fe{sub x}Mn{sub 1-x}O{sub 3} have been studied in the complete solid solution range 0.0<x<1.0. High temperature oxide melt drop solution calorimetry was performed to determine the enthalpies of formation from binary oxides and the enthalpy of mixing. There is a noticeable change in the energetics of the solid solution near x=0.7, which is due to the growing concentration of Fe{sup 4+} at higher Fe/(Fe+Mn) ratio. The balance between different valences of the transition metals, Mn and Fe, is the main factor in determining the energetics of the La{submore » 0.70}Sr{sub 0.30}Fe{sub x}Mn{sub 1-x}O{sub 3} solid solution. - Graphical abstract: Enthalpy of mixing ({Delta}H{sub mix}) of La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3-{gamma}} solid solution at room temperature as a function of Fe/(Fe+Mn) ratio, x. Linear fits for the two regions at low and high x are shown as solid lines. The inset shows the content of Mn{sup 3+}, Mn{sup 4+}, Fe{sup 3+} and Fe{sup 4+} as a function of x based on the work by Jonker. The redox reactions between different valence states of Fe and Mn dominate the energetic behavior of the solid solution. Highlights: > Investigated the structure, the energetics and the internal redox reactions of La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3}. > Determined the formation and mixing enthalpy by high temperature oxide melt solution calorimetry. > Symmetry of the perovskite, transition metal valence and energetics are interdependent. > Thermochemical data shows convincing evidence of the interplay between the Mn{sup 4+} and the Fe{sup 4+} ions. > Balance between different valences of Mn and Fe dominates the energetics of La{sub 0.7}Sr{sub 0.3}Fe{sub x}Mn{sub 1-x}O{sub 3}.« less
  • LiTiOAs{sub 1-} {sub x} P {sub x} O{sub 4} (0{<=}x{<=}1) compounds have been prepared using solutions of Li, Ti, As and P elements as starting products. Selected compositions have been investigated by powder X-ray or neutrons diffraction analysis, Raman and infrared spectroscopy. The structure of LiTiOAs{sub 1-} {sub x} P {sub x} O{sub 4} (x=0, 0.5 and 1) samples determined by Rietveld analysis is orthorhombic with Pnma space group. It is formed by a 3D network of TiO{sub 6} octahedra and XO{sub 4} (X=As{sub 1-} {sub x} P {sub x} ) tetrahedra where octahedral cavities are occupied by lithium atoms.more » TiO{sub 6} octahedra are linked together by corners and form infinite chains along a-axis. Ti atoms are displaced from the centre of octahedral units in alternating short (1.700-1.709 A) and long (2.301-2.275 A) Ti-O bonds. Raman and infrared studies confirm the existence of Ti-O-Ti chains. Thermal stability of LiTiOAsO{sub 4} has been reported. -- Graphical abstract: -Ti-O-Ti- chains and XO{sub 4} tetrahedra in LiTiOXO{sub 4} (X=As{sub 1-} {sub x} P {sub x} ) compounds.« less
  • The crystal structure of the La{sub 0.7}Ca{sub 0.3-x}Sr{sub x}CrO{sub 3} series, including the compositional and temperature dependence of the structural parameters, has been studied by variable temperature neutron diffraction measurements. The extent of the distortions from the ideal cubic perovskite structure has been evaluated quantitatively using the average bond lengths and the mean volumes of the [CrO{sub 6}] octahedron and [(La/Ca/Sr)O{sub 12}] polyhedron, and has been shown to decrease with increase of Sr content or temperature. At the structural phase transition from the orthorhombic (Pnma) structure to the rhombohedral (R3-barc) one, the volume of the [CrO{sub 6}] octahedron decreases whereasmore » that of the [(La/Ca/Sr)O{sub 12}] polyhedron shows little difference, resulting in an overall decrease in the level of distortion. The change in the degree of distortion at the phase transition decreases with increase of Sr content, in agreement with the smaller variation of the enthalpy and volume for the specimens with higher Sr content. - Graphical abstract: Temperature dependence of parameter, PHI, representing the extent of distortion from the ideal cubic perovskite structure, for La{sub 0.7}Ca{sub 0.3}CrO{sub 3} (diamonds) and La{sub 0.7}Ca{sub 0.15}Sr{sub 0.15}CrO{sub 3} (circles) calculated from neutron diffraction patterns.« less
  • The p-{rho}-T relationships and constant volume heat capacity C{sub v} were measured for binary hydrocarbon mixtures containing propane (C{sub 3}H{sub 8}) and isobutane (i-C{sub 4}H{sub 10}). Temperatures ranged from 200 K to 400 K for p-{rho}-T and from 203 K to 342 K for C{sub v} with pressures up to 35 MPa for both measurements. Measurements of p-{rho}-T and C{sub v} were conducted on liquid samples with the mole fraction compositions {l_brace}xC{sub 3}H{sub 8} + (1 {minus} x)i-C{sub 4}H{sub 10}{r_brace} for x = 0.7006 and x = 0.2979. Determinations of saturated-liquid densities were made by extrapolating each isochore to themore » saturated-liquid pressure and determining the temperature and density at the intersection. Published p-{rho}-T data are in good agreement with this study. For the p-{rho}-T apparatus, the uncertainty of the temperature is 0.03 K, and for pressure it is 0.01% at p > 3 MPa and 0.05% at p < 3 MPa. The principal source of uncertainty in density is the cell volume ({approximately}28.5 cm{sup 3}) with a standard uncertainty of 0.003 cm{sup 3}. When all components of experimental uncertainty are considered, the expanded relative uncertainty (with a coverage factor {kappa} = 2 and thus a two-standard-deviation estimate) of the density measurements is estimated to be 0.05%. For the C{sub v} apparatus, the uncertainty is 0.002 K for the temperature rise and 0.2% for the change-of-volume work, which is the principal source of uncertainty. The expanded relative uncertainty of the heat capacity measurements is estimated to be 0.7%. Hydrocarbon mixtures are considered to be leading candidates to replace chlorofluorocarbon refrigerants, which will be phased out under the terms of the Montreal Protocol.« less
  • The (NH{sub 4})[Fe(AsO{sub 4}){sub 1-x}(PO{sub 4}){sub x}F] (x=0.3, 0.6, 0.8) series of compounds has been synthesized under mild hydrothermal conditions. The compounds crystallize in the orthorhombic Pna2{sub 1} space group, with the unit-cell parameters a=13.1718(1), b=6.5966(6), c=10.797(1) A for x=0.3; a=13.081(1), b=6.5341(6), c=10.713(1) A for x=0.6 and a=13.0329(9), b=6.4994(4), c=10.6702(6) A for x=0.8, with the volumes 938.6(1), 915.7(1) and 903.8(1) A{sup 3}, respectively, with Z=8. Single crystals of (NH{sub 4})[Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.3}F] heated under air atmosphere at 465 deg. C remain as single crystals, changing the composition to Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.3}. This later phase belongs tomore » the orthorhombic Imam space group, with the unit cell parameters a=13.328(2), b=6.5114(5), c=10.703(1) A, V=928.9(2) A{sup 3} and Z=12. The crystal structure of the ammonium phases consists of a KTP three-dimensional framework constructed by chains formed by alternating Fe(2)O{sub 4}F{sub 2} or Fe(1)O{sub 4}F{sub 2} octahedra and As/P(2)O{sub 4} or As/P(1)O{sub 4} tetrahedra, respectively. These octahedra and tetrahedra are linked by a common oxygen vertex. The chains run along the 'a' and 'b' crystallographic axes. The crystal structure of Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.3} is a three-dimensional skeleton derived from that of the precursor, formed from (100) sheets stacked along the [001] direction, and interconnected by chains of alternating Fe(2)O{sub 6} octahedra and As/P(2)O{sub 4} tetrahedra sharing a vertex in the 'a' direction. Transmission electronic microscopy of this compound indicates the existence of unconnected external cavities with a BET surface area of 3.91(3) m{sup 2} g{sup -1}. The diffuse reflectance spectra in the visible region show the forbidden electronic transitions characteristic of the Fe(III) d{sup 5}-high spin cation in slightly distorted octahedral geometry, for all the compounds. The ESR spectra for all the compounds, carried out from room temperature to 4.2 K, remain isotropic with variation in temperature; the g-value is 1.99(1). Magnetic measurements indicate the predominance of antiferromagnetic interactions, with Neel temperatures near to 70.0 and 50.0 K for the ammonium phases and Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.30}, respectively. At low temperatures a spin canting phenomenon for Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.30} is detected. - Graphical abstract: The relationship between the |100| and |010| chains in (NH{sub 4})[Fe(AsO{sub 4}){sub 1-x}(PO{sub 4}){sub x}F] left and the |100| chains and the (001) sheets in Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.3}.« less