Structural, mechanical and electronic properties of 4d transition metal mononitrides by first-principles

Zhao, Erjun; Wang, Jinping; Meng, Jian; Wu, Zhijian

doi:10.1016/j.commatsci.2009.12.011

Cited by 73 publications

(20 citation statements)

References 54 publications

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“…The acoustic Debye temperature ( Θ ) is described as in which M is the molecular mass; Z is the number of atoms in the molecular formula; and k, h, N are Boltzmann’s constant, Planck’s constant, and Avogadro’s number, respectively. Using the experimentally determined elastic wave velocities and the density data at ambient condition ( V P = 8.79(2) km/s, V S = 4.91(1) km/s, ρ = 8.30(1) g/cm 3 ), the Debye temperature Θ 0 is determined to be 738 K, which is almost the same as Θ 0 = 737 K for NiAs-type NbN from theoretical calculations 16 and is also comparable to Θ 0 = 754 K for WC-type-structured NbN 16 .…”

Section: Discussionmentioning

confidence: 84%

“…The crystal structures of the transition-metal nitrides are generally characterized by strong intermetallic bonding with transition-metal atoms and N atoms occupying octahedral, tetrahedral or trigonal prismatic sites, giving rise to a large cohesive energy. It is known that NbN possesses many polymorphs 3 4 11 12 13 14 15 16 , but only cubic δ -NbN has been extensively investigated by different experimental techniques 3 4 and theoretical calculations 11 12 15 16 17 18 . Hardness measurements using the Vickers micro-indentation method were performed to study the mechanical properties of δ -NbN, yielding a Vickers hardness of 17~20 GPa as same as that of sapphire (18~20 GPa) 4 .…”

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confidence: 99%

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Hexagonal-structured ε-NbN: ultra-incompressibility, high shear rigidity and a possible hard superconducting material

Zou

Wang

Chen

et al. 2015

Sci Rep

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Exploring the structural stability and elasticity of hexagonal ε-NbN helps discover correlations among its physical properties for scientific and technological applications. Here, for the first time, we measured the ultra-incompressibility and high shear rigidity of polycrystalline hexagonal ε-NbN using ultrasonic interferometry and in situ X-ray diffraction, complemented with first-principles density-functional theory calculations up to 30 GPa in pressure. Using a finite strain equation of state approach, the elastic bulk and shear moduli, as well as their pressure dependences are derived from the measured velocities and densities, yielding BS0 = 373.3(15) GPa, G0 = 200.5(8) GPa, ∂BS/∂P = 3.81(3) and ∂G/∂P = 1.67(1). The hexagonal ε-NbN possesses a very high bulk modulus, rivaling that of superhard material cBN (B0 = 381.1 GPa). The high shear rigidity is comparable to that for superhard γ-B (G0 = 227.2 GPa). We found that the crystal structure of transition-metal nitrides and the outmost electrons of the corresponding metals may dominate their pressure dependences in bulk and shear moduli. In addition, the elastic moduli, Vickers hardness, Debye temperature, melting temperature and a possible superconductivity of hexagonal ε-NbN all increase with pressures, suggesting its exceptional suitability for applications under extreme conditions.

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Section: Discussionmentioning

confidence: 84%

mentioning

confidence: 99%

Hexagonal-structured ε-NbN: ultra-incompressibility, high shear rigidity and a possible hard superconducting material

Zou

Wang

Chen

et al. 2015

Sci Rep

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“…In order to determine the equilibrium lattice constant (a), we did a series of runs for each phase, varying the lattice constant in a range of 1Å around the estimated energy minimum configuration. This total energy versus volume data was fitted to the form of Birch-Murnaghan [48,49] equation of state as formulated by Zhao et al [50]. During each run, ions were allowed to fully relax within the symmetry constraints of space group P a3, while the cell shape and volume were fixed.…”

Section: A Methods For Structural and Mechanical Propertiesmentioning

confidence: 99%

Electronic and bonding analysis of hardness in pyrite-type transition-metal pernitrides

2014

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Most commonly known hard transition-metal nitrides crystallize in rocksalt structure (B1). The discovery of ultraincompressible pyrite-type PtN 2 10 years ago has raised a question about the cause of its exceptional mechanical properties. We answer this question by a systematic computational analysis of the pyrite-type PtN 2 and other transition-metal pernitrides (MN 2) with density functional theory. Apart from PtN 2 , the three hardest phases are found among them in the 3d transition-metal period. They are MnN 2 , CoN 2 , and NiN 2 , with computed Vickers hardness (H V) values of 19.9 GPa, 16.5 GPa, and 15.7 GPa, respectively. Harder than all of these is PtN 2 , with a H V of 23.5 GPa. We found the following trends and correlations that explain the origin of hardness in these pernitrides. (a) Charge transfer from M to N controls the length of the N-N bond, resulting in a correlation with bulk modulus, dominantly by providing Coulomb repulsion between the pairing N atoms. (b) Elastic constant C 44 , an indicator of mechanical stability and hardness is correlated with total density of states at E F , an indicator of metallicity. (c) Often cited monotonic variation of H V and Pugh's ratio with valence electron concentration found in rocksalt-type early transition-metal nitrides is not evident in this structure. (d) The change in MM bond strength under a shearing strain indicated by crystal orbital Hamilton population is predictive of hardness. This is a direct connection between a specific bond and shear related mechanical properties. This panoptic view involving ionicity, metallicity, and covalency is essential to obtain a clear microscopic understanding of hardness.

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“…More studies involving a systematic search throughout the transition metal region of the periodic table in many different structures have provided thorough data and organized knowledge to better explain and predict material properties. Among them, Zhao et al studied the structural, elastic and electronic properties of rocksalt-, NiAs-and WC-structured 4d transition metal mono-nitrides [19], and more structures of 5d transition metal mono-nitrides [20]. Patil et al [21] also investigated the 5d transition metal nitrides systematically, including zincblende, rocksalt, fluorite and pyrite structures, not limited to 1:1 stoichiometry.…”

Section: Introductionmentioning

confidence: 99%

Structural, mechanical and electronic properties of 3d transition metal nitrides in cubic zincblende, rocksalt and cesium chloride structures: a first-principles investigation

Liu¹,

Zhou²,

Khare³

et al. 2013

J. Phys.: Condens. Matter

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We report systematic results from ab initio calculations with density functional theory on three cubic structures, zincblende (zb), rocksalt (rs) and cesium chloride (cc), of the ten 3d transition metal nitrides. We computed lattice constants, elastic constants, their derived moduli and ratios that characterize mechanical properties. Experimental measurements exist in the literature of lattice constants for rs-ScN, rs-TiN and rs-VN and of elastic constants for rs-TiN and rs-VN, all of which are in good agreement with our computational results. Similarly, computed Vickers hardness (H V ) values for rs-TiN and rs-VN are consistent with earlier experimental results. Several trends were observed in our rich data set of 30 compounds. All nitrides, except for zb-CrN, rs-MnN, rs-FeN, cc-ScN, cc-CrN, cc-NiN and cc-ZnN, were found to be mechanically stable. A clear correlation in the atomic density with the bulk modulus (B) was observed with maximum values of B around FeN, MnN and CrN. The shear modulus, Young's modulus, H V and indicators of brittleness showed similar trends and all showed maxima for cc-VN. The calculated value of H V for cc-VN was about 30 GPa, while the next highest values were for rs-ScN and rs-TiN, about 24 GPa. A relation (H V ∝ θ 2 D ) between H V and Debye temperature (θ D ) was investigated and verified for each structure type. A tendency for anti-correlation of the elastic constant C 44 , which strongly influences stability and hardness, with the number of electronic states around the Fermi energy was observed.

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Structural, mechanical and electronic properties of 4d transition metal mononitrides by first-principles

Cited by 73 publications

References 54 publications

Hexagonal-structured ε-NbN: ultra-incompressibility, high shear rigidity and a possible hard superconducting material

Hexagonal-structured ε-NbN: ultra-incompressibility, high shear rigidity and a possible hard superconducting material

Electronic and bonding analysis of hardness in pyrite-type transition-metal pernitrides

Structural, mechanical and electronic properties of 3d transition metal nitrides in cubic zincblende, rocksalt and cesium chloride structures: a first-principles investigation

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