skip to main content

Title: The crystal structure of Hf{sub 1.5+{delta}}Nb{sub 1.5-{delta}}As and structure-composition relations in the section Hf{sub 3}As-Nb{sub 3}As

The title compound Hf{sub 1.5+{delta}}Nb{sub 1.5-{delta}}As was characterized by means of single crystal X-ray diffraction. It represents a new structure type of intermetallic compounds (space group Pnma; lattice parameters a=7.142(2) A, b=3.583(2) A, c=11.640(2) A) and shows a small homogeneity range corresponding to (0.1<delta<0.25) at 1400 deg. C. The crystal structure may be visualized by a combination of As-centred trigonal prisms of the metal atoms and bcc-like fragments formed by metal atoms. Structural relations with various binary arsenides are discussed. The structure of Hf{sub 1.5+{delta}}Nb{sub 1.5-{delta}}As shows significant preferred site occupation of Hf and Nb at the three independent metal positions (differential fractional site occupancy). Structure-composition relations in the section Hf{sub 3}As-Nb{sub 3}As which also contains the new phase Hf{sub 2+{delta}}Nb{sub 1-{delta}}As with Ti{sub 3}P-type structure (space group P4{sub 2}/n) are discussed. Ground state energies of various ordered compounds with Hf{sub 1.5+{delta}}Nb{sub 1.5-{delta}}As-, Ti{sub 3}P- and Ta{sub 3}As-type structures were calculated from ab initio density functional theory. These energies were used for thermodynamic calculations employing the compound energy formalism (CEF) with the aim to model the experimentally observed site fraction data for both ternary compounds as well as Gibbs energies at the temperature of equilibration (1400 deg. C). - Graphicalmore » abstract: Hf{sub 1.5+{delta}}Nb{sub 1.5-{delta}}As with a new structure type (space group Pnma; lattice parameters a=7.142(2) A, b=3.583(2) A, c=11.640(2)A) was synthesized. Phase relations, energies and partial ordering in the section Hf{sub 3}As-Nb{sub 3}As were studied by first principle DFT calculations and thermodynamic modelling.« less
Authors:
;  [1] ;  [1]
  1. Department of Inorganic Chemistry/Materials Chemistry, University of Vienna, Waehringerstr. 42, A-1090 Wien (Austria)
Publication Date:
OSTI Identifier:
21370354
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 182; Journal Issue: 4; Other Information: DOI: 10.1016/j.jssc.2009.01.020; PII: S0022-4596(09)00023-1; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; BCC LATTICES; DENSITY FUNCTIONAL METHOD; GROUND STATES; HAFNIUM ARSENIDES; INTERMETALLIC COMPOUNDS; LATTICE PARAMETERS; MONOCRYSTALS; NIOBIUM ARSENIDES; ORTHORHOMBIC LATTICES; SIMULATION; SPACE GROUPS; TETRAGONAL LATTICES; THERMODYNAMIC MODEL; X-RAY DIFFRACTION ALLOYS; ARSENIC COMPOUNDS; ARSENIDES; CALCULATION METHODS; COHERENT SCATTERING; CRYSTAL LATTICES; CRYSTAL STRUCTURE; CRYSTALS; CUBIC LATTICES; DIFFRACTION; ENERGY LEVELS; HAFNIUM COMPOUNDS; MATHEMATICAL MODELS; NIOBIUM COMPOUNDS; PARTICLE MODELS; PNICTIDES; REFRACTORY METAL COMPOUNDS; SCATTERING; STATISTICAL MODELS; SYMMETRY GROUPS; TRANSITION ELEMENT COMPOUNDS; VARIATIONAL METHODS