Publication detail

Point defects stabilise cubic Mo-N and Ta-N

KOUTNÁ, N. HOLEC, D. SVOBODA, O. KLIMASHIN, F. MAYRHOFER, P.

Original Title

Point defects stabilise cubic Mo-N and Ta-N

Type

journal article in Web of Science

Language

English

Original Abstract

We employab initio calculations to investigate energetics of point defects in metastable rocksalt cubic Ta-N and Mo-N. Our results reveal a strong tendency to off-stoichiometry, i.e. defected structures are predicted to be more stable than perfect ones with 1:1 metal-to-nitrogen stoichiometry, in agreement with previous literature reports. While Ta-N significantly favours metal vacancies, Mo-N exhibits similar energies of formation regardless of the vacancy type (V Mo , V N ) as long as their concentration is below ?15at.\% . The overall lowest energy of formation were obtained for Ta 0.78 N and Mo 0.91 N , which are hence predicted to be the most stable compositions. To account for various experimental condition during synthesis, we further evaluated the phase stability as a function of chemical potential of individual species. The proposed phase diagrams reveal four stable compositions, Mo 0.84 N , Mo 0.91 N , MoN 0.69 and MoN 0.44 , in the case of Mo-N and nine stable compositions in the case of Ta-N indicating the crucial role of metal under-stoichiometry, since Ta 0.75 N and Ta 0.78 N significantly dominate the diagram. These results are important for understanding and designing experiments using non-equilibrium deposition techniques. Finally, we discuss a role of defects ordering and estimate a cubic lattice parameter as a function of a defect contents.

Keywords

Mo-N;Ta-N;point defects;vacancies;stability;DFT

Authors

KOUTNÁ, N.; HOLEC, D.; SVOBODA, O.; KLIMASHIN, F.; MAYRHOFER, P.

Released

22. 8. 2016

Publisher

IOP PUBLISHING LTD

Location

TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND

ISBN

0022-3727

Periodical

Journal of Physics D: Applied Physics

Year of study

49

Number

37

State

United Kingdom of Great Britain and Northern Ireland

Pages from

1

Pages to

8

Pages count

8

URL

http://dx.doi.org/10.1088/0022-3727/49/37/375303

Full text in the Digital Library

http://hdl.handle.net/11012/203171

BibTex

@article{BUT127123,
  author="Nikola {Koutná} and David {Holec} and Ondřej {Svoboda} and Fedor {Klimashin} and Paul {Mayrhofer}",
  title="Point defects stabilise cubic Mo-N and Ta-N",
  journal="Journal of Physics D: Applied Physics",
  year="2016",
  volume="49",
  number="37",
  pages="1--8",
  doi="10.1088/0022-3727/49/37/375303",
  issn="0022-3727",
  url="http://dx.doi.org/10.1088/0022-3727/49/37/375303"
}