Elastic Properties of Some Polycrystalline Transition-Metal Monocarbides

Brown, H.L.; Armstrong, P.E.; Kempter, Charles P.

doi:10.1063/1.1727602

Cited by 147 publications

(63 citation statements)

References 7 publications

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“…30 and we generalized the result for the case of an uniaxial substrate (see the Appendix for details). There are two specially relevant cases for the behavior of 0 (q,ω): 33 /ρ 3D for the uniaxial case), and ω = 0, for which…”

Section: 27mentioning

confidence: 99%

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Flexural mode of graphene on a substrate

2013

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Out of plane vibrations are suppressed in graphene layers placed on a substrate. These vibrations, in suspended samples, are relevant for the understanding of properties such as the electrical resistivity, the thermal expansion coefficient, and others. We use a general framework to study the properties of the out of plane mode in graphene on different substrates, taking into account the dynamics of the substrate. We discuss broadening of this mode and how it hybridizes with the substrate Rayleigh mode, comparing our model with experimental observations. We use the model to estimate the substrate induced changes in the thermal expansion coefficient and in the temperature dependence of the electrical resistivity.

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Section: 27mentioning

confidence: 99%

“…1(b), where we show a density plot of the spectral function along with the dispersion of the fR mode. The gap of the fG mode is controlled by ω 0 = √ g/ρ 2D , while the broadening is controlled by 33 /ρ 3D for the uniaxial case). For g = 1.82 × 10 20 J/m 4 one obtains ω 0 ≈ 10 meV and γ 0 ≈ 13 THz for graphene on SiO 2 .…”

Section: 27mentioning

confidence: 99%

Flexural mode of graphene on a substrate

2013

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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.…”

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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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“…The binding energy between two interstitial hydrogen atoms is negative, suggesting a Reference [22] b Reference [23] c Reference [24] d Reference [25] , eV). …”

Section: Resultsmentioning

confidence: 99%

First principles study of hydrogen behaviors in hexagonal tungsten carbide

Kong

You

Liu

et al. 2011

Journal of Nuclear Materials

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Understanding the behavior of hydrogen in hexagonal tungsten carbide (WC) is of particular interest for fusion reactor design due to the presence of WC in the divertor of fusion reactors. Therefore, we use first-principles calculations to study the hydrogen behavior in WC. The most stable interstitial site for the hydrogen atom is the projection of the octahedral interstitial site on tungsten basal plane, followed by the site near the projection of the octahedral interstitial site on carbon basal plane. The binding energy between two interstitial hydrogen atoms is negative, suggesting that hydrogen itself is not capable of trapping other hydrogen atoms to form a hydrogen molecule. The calculated results on the interaction between hydrogen and vacancy indicate that the hydrogen atom is energetically trapped by vacancy and the hydrogen molecule can not be formed in mono-vacancy. In addition, the hydrogen atom bound to carbon is only found in tungsten vacancy. We also study the migrations of hydrogen in WC and find that the interstitial hydrogen atom 0 *Author to whom correspondence should be addressed.Email address: csliu@issp.ac.cn Tel: 0086-551-5591062Preprint submitted to Journal of Nuclear Materials February 26, 2018 prefers to diffusion along the c axis. Our studies on the hydrogen behavior in WC provide some explanations for the experimental results of the thermal desorption process of energetic hydrogen ion implanted into WC.

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Elastic Properties of Some Polycrystalline Transition-Metal Monocarbides

Abstract: Articles you may be interested inElectronic transport properties on transition-metal terminated zigzag graphene nanoribbons Magnetic properties of 3d transitionmetal dichalcogenides with the pyrite structure

Cited by 147 publications

References 7 publications

Flexural mode of graphene on a substrate

Flexural mode of graphene on a substrate

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

First principles study of hydrogen behaviors in hexagonal tungsten carbide

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