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Correlating structure and orbital occupation with the stability and mechanical properties of 3d transition metal carbides.

Authors :
Khatri, I.
Szymanski, N.J.
Dumre, B.B.
Amar, J.G.
Gall, D.
Khare, S.V.
Source :
Journal of Alloys & Compounds. Jan2022, Vol. 891, pN.PAG-N.PAG. 1p.
Publication Year :
2022

Abstract

The development of novel transition metal carbides for improved hard coating technologies requires a detailed understanding of the factors influencing their stability and mechanical performance. To this end, we carried out first principles calculations based on density functional theory to tabulate the electronic structures, formation energies, and phonon dispersion curves of 3d transition metal carbides adopting zincblende, rocksalt, and cesium chloride structures. By analyzing the corresponding results, we outline a theoretical framework that describes how valence electron concentration and bonding configuration control the stability of these compounds. Many early transition metal carbides are predicted to be stable in the rocksalt and zincblende structures, enabled by filled bonding states, whereas the cesium chloride structure shows persistent instability. For compounds that are predicted to be stable, mechanical properties were investigated through calculation of elastic tensors, from which observable properties including Vicker's hardness and ductility were derived. A robust mechanical performance is shown to be correlated with complete filling of bonding orbitals as illustrated for rocksalt TiC and VC, which have calculated hardnesses of 25.66 and 22.63 GPa respectively. However, enhanced ductility and toughness can be achieved by allowing partial occupation of the antibonding states as in CrC, which has a relatively low Pugh's ratio of 0.51. [Display omitted] • Early 3d transition metal carbides show robust stability and high hardness. • Complete filling of bonding orbitals is crucial to maintain stability. • Partial antibonding contributes to decreased hardness but enhanced ductility. • Overoccupied antibonding orbitals cause instabilities in the rocksalt structure. • Jahn-Teller distortions cause instabilities in the zincblende structure. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
09258388
Volume :
891
Database :
Academic Search Index
Journal :
Journal of Alloys & Compounds
Publication Type :
Academic Journal
Accession number :
153371667
Full Text :
https://doi.org/10.1016/j.jallcom.2021.161866