Premium
Vacancy ordering in VN 1−x
Author(s) -
Onozuka T.
Publication year - 1978
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889878012893
Subject(s) - tetragonal crystal system , superstructure , vacancy defect , crystallography , crystal structure , phase diagram , lattice constant , condensed matter physics , chemistry , diffraction , materials science , phase (matter) , thermodynamics , physics , organic chemistry , optics
An ordered structure is found in the composition range VN 0.74 – VN 0.84 of the cubic mononitride phase by means of electron diffraction/microscopy. The lattice constant of this structure is twice as large as that of the original NaCl type cell. At the composition VN 0.81 , or V 32 N 26 , six nitrogen atoms are missing from the unit cell. The vacancy arrangement has tetragonal symmetry, and the superstructure belongs to the space group P 4 2 / nmc . Disordering of this structure occurs at about 520 °C. The transition entropy determined from heat‐capacity measurements agrees well with a calculation based on the crystal structure proposed here. A tentative phase diagram for the composition range VN 0.6 – VN 1.0 is presented.