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

Journal Article · Wed Apr 15 04:00:00 EDT 2009 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.01.020· OSTI ID:21370354

Warczok, Piotr; Chumak, Igor ^[1]

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1. Department of Inorganic Chemistry/Materials Chemistry, University of Vienna, Waehringerstr. 42, A-1090 Wien (Austria)

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). - Graphical 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.

• OSTI ID: 21370354
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 4 Vol. 182; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ALLOYS
ARSENIC COMPOUNDS
ARSENIDES
BCC LATTICES
CALCULATION METHODS
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
CUBIC LATTICES
DENSITY FUNCTIONAL METHOD
DIFFRACTION
ENERGY LEVELS
GROUND STATES
HAFNIUM ARSENIDES
HAFNIUM COMPOUNDS
INTERMETALLIC COMPOUNDS
LATTICE PARAMETERS
MATHEMATICAL MODELS
MONOCRYSTALS
NIOBIUM ARSENIDES
NIOBIUM COMPOUNDS
ORTHORHOMBIC LATTICES
PARTICLE MODELS
PNICTIDES
REFRACTORY METAL COMPOUNDS
SCATTERING
SIMULATION
SPACE GROUPS
STATISTICAL MODELS
SYMMETRY GROUPS
TETRAGONAL LATTICES
THERMODYNAMIC MODEL
TRANSITION ELEMENT COMPOUNDS
VARIATIONAL METHODS
X-RAY DIFFRACTION