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Electronic Structure and Stability of Ordered Vacancy Phases of NbN

Published online by Cambridge University Press:  10 February 2011

E. C. Ethridge ,
S. C. Erwin  and
W. E. Pickett
E. C. Ethridge
Affiliation:
Complex Systems Theory Branch, Naval Research Laboratory, Washington DC 20375
S. C. Erwin
Affiliation:
Complex Systems Theory Branch, Naval Research Laboratory, Washington DC 20375
W. E. Pickett
Affiliation:
Complex Systems Theory Branch, Naval Research Laboratory, Washington DC 20375
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Abstract

A recently reported metastable phase of NbN with a superconducting Tc=16.4 K is characterized using full potential electronic structure methods. This new phase, which has Pm3m (cubic) symmetry, can be described as the B1 (rocksalt) structure with 25% ordered vacancies on each sublattice. We compare the equation of state and electronic spectrum of this Pm3m phase with its rocksalt counterpart [1] and with Nb4N3 in the 14/mmm (tetragonal) phase, which allows the characterization of N vacancies without accompanying Nb vacancies. For Pm3m NbN, the calculated lattice constant is 5% smaller than reported and the energy is 1.00 eV/molecule higher than B1 NbN, suggesting that the newly reported phase is something other than a stoichiometric Pm3m phase of NbN. We report on the energy surface for tetragonal distortions of this phase, from which we evaluate its structural stability and obtain Poisson's ratio.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 408: Symposium P – Materials Theory, Simulations, and Parallel Algorithms , 1995 , 545
Copyright
Copyright © Materials Research Society 1996

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