Point defects stabilise cubic Mo-N and Ta-N

J 2016

Point defects stabilise cubic Mo-N and Ta-N

KOUTNÁ, Nikola, David HOLEC, Ondřej SVOBODA, Fedor KLIMASHIN, Paul MAYRHOFER et. al.

Basic information

Original name

Point defects stabilise cubic Mo-N and Ta-N

Authors

KOUTNÁ, Nikola (203 Czech Republic, belonging to the institution), David HOLEC (203 Czech Republic, guarantor), Ondřej SVOBODA (203 Czech Republic), Fedor KLIMASHIN (643 Russian Federation) and Paul MAYRHOFER (40 Austria)

Edition

JOURNAL OF PHYSICS D-APPLIED PHYSICS, Bristol, IOP Publishing Ltd, 2016, 0022-3727

Other information

Language

English

Type of outcome

Článek v odborném periodiku

Field of Study

10302 Condensed matter physics

Country of publisher

United Kingdom of Great Britain and Northern Ireland

Confidentiality degree

není předmětem státního či obchodního tajemství

References:

Full Text

Impact factor

Impact factor: 2.588

RIV identification code

RIV/00216224:14310/16:00091306

Organization unit

Faculty of Science

DOI

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

UT WoS

000384093000022

Keywords in English

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

Abstract

V originále

We employ ab 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 surprisingly predicted to be more stable than perfect ones with 1 : 1 metal-to-nitrogen stoichiometry. Despite the similarity of Ta-N and Mo-N systems in exhibiting this unusual behaviour, we also point out their crucial differences. 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 approximate to 15 at.%. The overall lowest energies of formation were obtained for Ta0.78N and Mo0.91N, which are hence predicted to be the most stable compositions. To account for various experimental conditions 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, Mo0.84N, Mo0.91N, MoN0.69 and MoN0.44, in the case of Mo-N and nine stable compositions in the case of Ta-N indicating the important role of metal under-stoichiometry, since Ta0.75N and Ta0.78N significantly dominate the diagram. This is particularly important for understanding and designing experiments using non-equilibrium deposition techniques. Finally, we discuss the role of defect ordering and estimate a cubic lattice parameter as a function of defect contents and put them in the context of existing literature theoretical and experimental data.

Links

LM2010005, research and development project

Name: Velká infrastruktura CESNET (Acronym: VI CESNET)

Investor: Ministry of Education, Youth and Sports of the CR

Citovat

KOUTNÁ, Nikola, David HOLEC, Ondřej SVOBODA, Fedor KLIMASHIN and Paul MAYRHOFER. Point defects stabilise cubic Mo-N and Ta-N. JOURNAL OF PHYSICS D-APPLIED PHYSICS. Bristol: IOP Publishing Ltd, 2016, vol. 49, No 37, p. 1-8. ISSN 0022-3727. Available from: https://dx.doi.org/10.1088/0022-3727/49/37/375303.

@article{1357491,
   author = {Koutná, Nikola and Holec, David and Svoboda, Ondřej and Klimashin, Fedor and Mayrhofer, Paul},
   article_location = {Bristol},
   article_number = {37},
   doi = {http://dx.doi.org/10.1088/0022-3727/49/37/375303},
   keywords = {Mo-N; Ta-N; point defects; vacancies; stability; DFT},
   language = {eng},
   issn = {0022-3727},
   journal = {JOURNAL OF PHYSICS D-APPLIED PHYSICS},
   title = {Point defects stabilise cubic Mo-N and Ta-N},
   url = {https://iopscience.iop.org/article/10.1088/0022-3727/49/37/375303/pdf},
   volume = {49},
   year = {2016}
}

TY  - JOUR
ID  - 1357491
AU  - Koutná, Nikola - Holec, David - Svoboda, Ondřej - Klimashin, Fedor - Mayrhofer, Paul
PY  - 2016
TI  - Point defects stabilise cubic Mo-N and Ta-N
JF  - JOURNAL OF PHYSICS D-APPLIED PHYSICS
VL  - 49
IS  - 37
SP  - 1-8
EP  - 1-8
PB  - IOP Publishing Ltd
SN  - 00223727
KW  - Mo-N
KW  - Ta-N
KW  - point defects
KW  - vacancies
KW  - stability
KW  - DFT
UR  - https://iopscience.iop.org/article/10.1088/0022-3727/49/37/375303/pdf
L2  - https://iopscience.iop.org/article/10.1088/0022-3727/49/37/375303/pdf
N2  - We employ ab 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 surprisingly predicted to be more stable than perfect ones with 1 : 1 metal-to-nitrogen stoichiometry. Despite the similarity of Ta-N and Mo-N systems in exhibiting this unusual behaviour, we also point out their crucial differences. 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 approximate to 15 at.%. The overall lowest energies of formation were obtained for Ta0.78N and Mo0.91N, which are hence predicted to be the most stable compositions. To account for various experimental conditions 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, Mo0.84N, Mo0.91N, MoN0.69 and MoN0.44, in the case of Mo-N and nine stable compositions in the case of Ta-N indicating the important role of metal under-stoichiometry, since Ta0.75N and Ta0.78N significantly dominate the diagram. This is particularly important for understanding and designing experiments using non-equilibrium deposition techniques. Finally, we discuss the role of defect ordering and estimate a cubic lattice parameter as a function of defect contents and put them in the context of existing literature theoretical and experimental data.
ER  -

KOUTNÁ, Nikola, David HOLEC, Ondřej SVOBODA, Fedor KLIMASHIN and Paul MAYRHOFER. Point defects stabilise cubic Mo-N and Ta-N. \textit{JOURNAL OF PHYSICS D-APPLIED PHYSICS}. Bristol: IOP Publishing Ltd, 2016, vol.~49, No~37, p.~1-8. ISSN~0022-3727. Available from: https://dx.doi.org/10.1088/0022-3727/49/37/375303.

Detailed Information on Publication Record