Abstract
Owing to exploring the influence of the N atoms ordering in Ta2N compounds on their properties, the stability, elastic, and electronic properties of Ta2N compounds (Ta2N-I: P3¯ml and Ta2N-II: P3¯1m) were investigated using first-principles calculations based on density functional theory. Ta2N-II is energetically favorable according to the enthalpy of formation. Elastic constants were employed to reveal the stronger resistance to deformation, but weaker anisotropy, in Ta2N-II. A ductile-brittle transition was found between Ta2N-I (ductile) and Ta2N-II (brittle). The partial density of states showed a stronger orbital hybridization of Ta-d and N-p in Ta2N-II, resulting in stronger covalent bonding. The charge density difference illustrated the interaction of the Ta-N bond and electron distribution of Ta2N.
Highlights
The transition metal nitrides (TMNs) have widespread applications and motivate intense research because of their outstanding properties, such as good mechanical, thermal stability, electronic, and optical properties [1,2,3,4,5,6]
The calculated lattice parameters (a = 3.110 Å, c = 4.896 Å) of Ta2N-I were very close to the results (a = 3.11 Å, c = 4.88 Å) [24] calculated through the same pseudo-potential (GGA-PBE), which confirms the reliability of this work
The calculated lattice parameters, enthalpies of formation, and elastic constants were a good match with the references, which confirms the reliability of our calculations
Summary
The transition metal nitrides (TMNs) have widespread applications and motivate intense research because of their outstanding properties, such as good mechanical, thermal stability, electronic, and optical properties [1,2,3,4,5,6]. Terao et al [14] detected hexagonal close-packed γ-Ta2N (Ta2N-I), called β-Ta2N, with lattice parameters a = 3.05 Å, c = 4.92 Å (Space group, No.164) through XRD They discovered the other structure of Ta2N (Ta2N-II) with lattice parameters a = 5.28 Å, c = 4.92 Å (Space group, No.162), due to a different ordering of N atoms, characterized by electron diffraction, which can display many weak peaks invisible in XRD. As the characterization techniques developed, neutron diffraction was employed by Conroy and Christensen to further confirm this structure (Ta2N-II) [19]. It is because of the ordering of vacancies that Ta2N-II come into being, which was presented by Friedrich et al [20]
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