Hard superconducting nitrides

Chen, Xiao‐Jia; Struzhkin, Viktor V.; Wu, Zhigang; Somayazulu, Maddury; Qian, Jiangu; Kung, Simon; Christensen, A. Nørlund; Zhao, Yusheng; Cohen, R. E.; Mao, Ho‐kwang; Hemley, Russell J.

doi:10.1073/pnas.0500174102

Cited by 276 publications

(189 citation statements)

References 30 publications

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“…2,3,6,[9][10][11][12] The extrapolated bulk moduli of HP-LaN with values of 278.5(6.4) and 293.2(7.2) GPa are extremely high, ranking HP-LaN as a highly incompressible material comparable to d-ZrN or dHfN having bulk moduli of 285 GPa and 306 GPa, respectively. 38 As expected, the high-pressure phase is less compressible than the ambient phase and shows a smaller first pressure derivative of the bulk modulus. This corresponds to the usually expected behavior as the repulsive forces of atoms become stronger at higher pressure.…”

Section: -4mentioning

confidence: 78%

Reversible high-pressure phase transition in LaN

Schneider¹,

Baumann²,

Salamat³

et al. 2012

Journal of Applied Physics

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In situ high-pressure X-ray powder diffraction experiments on LaN up to 60.1 GPa at ambient temperature in a diamond-anvil cell revealed a reversible, first-order structural phase transition starting at $22.8 GPa and completed at $26.5 GPa from the ambient cubic phase (Fm 3m, no. 225) to a tetragonal high-pressure phase (P4/nmm, no. 19, a ¼ 4.1060(6), c ¼ 3.0446(6) Å , Z ¼ 2, wR p ¼ 0.011), which has not been claimed in theoretical predictions. HP-LaN is isotypic with a high-pressure polymorph of BaO, which crystallizes in a tetragonally distorted CsCl-type structure. The phase transition is accompanied by a volume collapse of about 11% which corresponds well with the reported data on HP-BaO. A linear extrapolation of the c/a ratio of the tetragonally distorted CsCl-type sub-cell reaches a value c/a ¼ 1 of cubic CsCl-type HP-LaN at 91(12) GPa. In addition, the compressibility of LaN was investigated and resulted in a bulk modulus for the ambient pressure phase of

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Section: -4mentioning

confidence: 78%

Reversible high-pressure phase transition in LaN

Schneider¹,

Baumann²,

Salamat³

et al. 2012

Journal of Applied Physics

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“…7 Nitrides are a particularly compelling class of materials to explore computationally, 8−11 as they are rare in nature and difficult to synthesize in the laboratory. They also have significant technological relevance, as the unique bonding characteristics in nitrides yield electronic structures that range from metallic to semiconducting, producing materials with properties relevant to applications spanning refractory ceramics, 12,13 superconductors, 14,15 solid-state lighting, 16,17 photovoltaics, 18,19 photocatalysts, 20,21 thermoelectrics, 22,23 piezoelectrics, 24,25 permanent magnets, 26 and more.…”

Section: ■ Introductionmentioning

confidence: 99%

Thermodynamic Routes to Novel Metastable Nitrogen-Rich Nitrides

et al. 2017

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Compared to oxides, the nitrides are relatively unexplored, making them a promising chemical space for novel materials discovery. Of particular interest are nitrogen-rich nitrides, which often possess useful semiconducting properties for electronic and optoelectronic applications. However, such nitrogen-rich compounds are generally metastable, and the lack of a guiding theory for their synthesis has limited their exploration. Here, we review the remarkable metastability of observed nitrides, and examine the thermodynamics of how reactive nitrogen precursors can stabilize metastable nitrogen-rich compositions during materials synthesis. We map these thermodynamic strategies onto a predictive computational search, training a data-mined ionic substitution algorithm specifically for nitride discovery, which we combine with grand-canonical DFT-SCAN phase stability calculations to compute stabilizing nitrogen chemical potentials. We identify several new nitrogen-rich binary nitrides for experimental investigation, notably the transition metal nitrides Mn 3 N 4 , Cr 3 N 4 , V 3 N 4 , and Nb 3 N 5 , the main group nitride SbN, and the pernitrides FeN 2 , CrN 2 , and Cu 2 N 2 . By formulating rational thermodynamic routes to metastable compounds, we expand the search space for functional technological materials beyond equilibrium phases and compositions.

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“…Equilibrium lattice constants a 0 and bulk moduli B were evaluated from fitting energy and volume data to the Vinet equation of state [18]. Compared with the available experimental data [6,19,20,21], a 0 are about 1.0-1.5% smaller, while in average B are 15% larger. These are typical LDA errors.…”

mentioning

confidence: 99%

Trends in elasticity and electronic structure of transition-metal nitrides and carbides from first principles

et al. 2005

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The elastic properties of the B1-structured transition-metal nitrides and their carbide counterparts are studied using the ab initio density functional perturbation theory. The linear response results of elastic constants are in excellent agreement with those obtained from numerical derivative methods, and are also consistent with measured data. We find the following trends: (1) Bulk moduli B and tetragonal shear moduli G ′ = (C11 − C12)/2, increase and lattice constants a0 decrease rightward or downward on the Periodic Table for the metal component or if C is replaced by N; (2) The inequality B > G ′ > G > 0 holds for G = C44; (3) G depends strongly on the number of valence electrons per unit cell (ZV ). From the fitted curve of G as a function of ZV , we can predict that MoN is unstable in B1 structure, and transition-metal carbonitrides (e.g. ZrCxN1−x) and di-transition-metal carbides (e.g. HfxTa1−xC) have maximum G at ZV ≈ 8.3.PACS numbers: 62.20. Dc, 71.15.Mb, 74.70.Ad Elasticity describes the response of a crystal under external strain and provides key information of the bonding strength between nearest-neighbor atoms. The information obtained from accurate calculation of elasticity is essential for understanding the macroscopic mechanical properties of solids and for the design of hard materials. Nowadays it is possible to calculate elasticity using ab initio quantum-mechanical techniques, and ab initio calculations have proven to be very powerful in not only providing accurate elastic constants or moduli in good agreement with measurements [1] but also predicting elasticity at extreme conditions of high temperatures and high pressures [2,3], which are not easily accessible to experiment but have wide applications in the fields ranging from solid-state physics to seismology. Most previous ab initio calculations of elasticity used finite strain methods within the framework of the density-functional theory (DFT). The development of density-functional perturbation theory (DFPT) makes it possible now to obtain elastic constants directly and more accurately [4,5].Transition-metal nitrides and carbides in the rocksalt (B 1 ) structure are widely used for cutting tools, magnetic storage devices, generators and maglev trains due to their high hardness, high melting points and oxidation resistance [6]. These excellent properties are associated with their unusual electronic bonding. The relatively high superconducting transition temperature in some of these compounds, reaching nearly 18 K in NbC 1−x N x [8], indicates a strong electron-phonon interaction. Many theoretical studies of their electronic structure [7,9,10,11,12,13] have revealed an unusual mixture of covalent, metallic, and ionic contributions to bonding which must ultimately lie at the root of their unusual properties. Specifically, it was found [11] that the hardness enhancement of these materials can be understood on a fundamental level in terms of their electronic band structures. But the general trends of elasticity and electronic structure amon...

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Hard superconducting nitrides

Cited by 276 publications

References 30 publications

Reversible high-pressure phase transition in LaN

Reversible high-pressure phase transition in LaN

Thermodynamic Routes to Novel Metastable Nitrogen-Rich Nitrides

Trends in elasticity and electronic structure of transition-metal nitrides and carbides from first principles

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