First-principles calculations of hydrostatic pressure effects on the structural, elastic and thermodynamic properties of cubic monocarbides XC (X = Ti, V, Cr, Nb, Mo, Hf)
TL;DR: In this paper, a detailed comparative ab initio study of six transition metal monocarbides (TiC, VC, CrC, NbC, MoC, HfC) with the rock-salt structure was performed for a detailed comparison of their structural, electronic, elastic, and thermodynamic properties at ambient and elevated up to 50 GPa hydrostatic pressures.
About: This article is published in Solid State Sciences.The article was published on 2012-10-01. It has received 40 citations till now. The article focuses on the topics: Hydrostatic pressure.
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25 Apr 2019
TL;DR: In this paper, a thorough treatment of ultra-high temperature materials with melting points around or over 2500 °C is presented, which can be applied in various engineering devices and environmental conditions in the wide range from cryogenic to ultra high temperatures, on the basis of the latest updates in the field of physics, chemistry, nanotechnology, materials science and engineering.
Abstract: The work represents a thorough treatment of ultra-high temperature materials with melting points around or over 2500 °C. The second volume included physical (structural, thermal, electromagnetic, optical, mechanical and nuclear) and chemical (binary, ternary and multicomponent systems, solid-state diffusion, wettability, interaction with chemicals, gases and aqueous solutions) properties of refractory carbide materials: tantalum carbides (monocarbide TaC1–x and semicarbide a/b-Ta2±xC), hafnium monocarbide HfC1–x, niobium carbides (monocarbide NbC1–x and semicarbide a/b/c-Nb2±xC) and zirconium monocarbide ZrC1–x. It will be of interest to researchers, engineers, postgraduate, graduate and undergraduate students alike. The reader/user is provided with the full qualitative and quantitative assessment for the materials, which could be applied in various engineering devices and environmental conditions in the wide range from cryogenic to ultra-high temperatures, on the basis of the latest updates in the field of physics, chemistry, nanotechnology, materials science and engineering.
106 citations
Cites background or methods from "First-principles calculations of hy..."
...Some recent works [152, 356, 402, 409, 738, 955] are devoted to the calculations of coefficients of thermal expansion of niobium carbides by means of theoretical modelling....
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...longitudinal velocity VS, m s −1 8600 [396], 8562 [366, 396, 398], 8698 [375, 396], 8918 (0 K) [402], 7738 (*300 K) [402], 7320 [399], 8440–8570 [409], 8152 [404], 8861 [926]; transversal velocity VT, m s −1 5119 [396], 4722 [366, 396, 398], 5013 [375, 396], 4960 (0 K) [402], 4261 (*300 K) [402], 3920 [399], 5020–5200 [409], 4615 [404], 5420 [926]; average velocity Vm, m s −1 5662 [396], 5258 [366, 396, 398], 5562 [375, 396], 4370 [399], 5560–5740 [409], 5133 [404], 5975 [926];...
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...23 [404, 405] 644 129 166 – 302 – [393] 646 127 192 406–604 300 – [409] 593 140 176 365–539 291 – [409]...
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...5190 (4920) [410] 5670 (5400) [32, 45] Enthalpy (heat) of complete dissociation (atomization) from solid state at 298,15 K (−DatH°298, kJ mol): 1546 ± 12 [1], 1640 [51], 1627 [409], 1674 [57], 1570 ± 10 [579] Carbon content – 48....
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...– – – – 311–336 – [409] – – – 310 – – [727] 593 126 132 428 281 0....
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TL;DR: In this article, the structural stability and mechanical properties of Niobium carbide (NbC) were characterized by combined experimental methods and first-principles technique and the hardness and Young's modulus were measured to be 24.5 GPa and 406 GPa for NbC from nanoindentation, respectively.
59 citations
TL;DR: In this paper, the crystal structure, cohesive energy, formation enthalpy, mechanical anisotropy, electronic properties and hardness of molybdenum carbide are investigated by the first-principles calculations.
Abstract: The crystal structure, cohesive energy, formation enthalpy, mechanical anisotropy, electronic properties and hardness of α−MoC, β−MoC and γ−MoC are investigated by the first-principles calculations. The elastic constants and the bulk moduli, shear moduli, Young's moduli are calculated. The Young's modulus values of α−MoC, β−MoC and γ−MoC are 395.6 GPa, 551.2 GPa and 399.5 GPa, respectively. The surface constructions of Young's moduli identify the mechanical anisotropy of molybdenum carbide, and the results show that anisotropy of α−MoC is stronger than others. The electronic structure indicates that the bonding behaviors of MoC are the combinations of covalent and metallic bonds. The hardness of β−MoC is obviously higher than those of α−MoC and γ−MoC.
50 citations
TL;DR: In this paper, the elastic, thermophysical and thermochemical properties of the rock salt-type transition metal carbides and nitrides are investigated and compared with corresponding experimental data and a good agreement is seen.
49 citations
TL;DR: In this article, the authors have reported the synthesis of molybdenum carbide (MoC/Mo2C) via in-situ carburization route.
48 citations
References
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TL;DR: A simple derivation of a simple GGA is presented, in which all parameters (other than those in LSD) are fundamental constants, and only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked.
Abstract: Generalized gradient approximations (GGA’s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. [S0031-9007(96)01479-2] PACS numbers: 71.15.Mb, 71.45.Gm Kohn-Sham density functional theory [1,2] is widely used for self-consistent-field electronic structure calculations of the ground-state properties of atoms, molecules, and solids. In this theory, only the exchange-correlation energy EXC › EX 1 EC as a functional of the electron spin densities n"srd and n#srd must be approximated. The most popular functionals have a form appropriate for slowly varying densities: the local spin density (LSD) approximation Z d 3 rn e unif
146,533 citations
TL;DR: In this paper, the self-interaction correction (SIC) of any density functional for the ground-state energy is discussed. But the exact density functional is strictly selfinteraction-free (i.e., orbitals demonstrably do not selfinteract), but many approximations to it, including the local spin-density (LSD) approximation for exchange and correlation, are not.
Abstract: The exact density functional for the ground-state energy is strictly self-interaction-free (i.e., orbitals demonstrably do not self-interact), but many approximations to it, including the local-spin-density (LSD) approximation for exchange and correlation, are not. We present two related methods for the self-interaction correction (SIC) of any density functional for the energy; correction of the self-consistent one-electron potenial follows naturally from the variational principle. Both methods are sanctioned by the Hohenberg-Kohn theorem. Although the first method introduces an orbital-dependent single-particle potential, the second involves a local potential as in the Kohn-Sham scheme. We apply the first method to LSD and show that it properly conserves the number content of the exchange-correlation hole, while substantially improving the description of its shape. We apply this method to a number of physical problems, where the uncorrected LSD approach produces systematic errors. We find systematic improvements, qualitative as well as quantitative, from this simple correction. Benefits of SIC in atomic calculations include (i) improved values for the total energy and for the separate exchange and correlation pieces of it, (ii) accurate binding energies of negative ions, which are wrongly unstable in LSD, (iii) more accurate electron densities, (iv) orbital eigenvalues that closely approximate physical removal energies, including relaxation, and (v) correct longrange behavior of the potential and density. It appears that SIC can also remedy the LSD underestimate of the band gaps in insulators (as shown by numerical calculations for the rare-gas solids and CuCl), and the LSD overestimate of the cohesive energies of transition metals. The LSD spin splitting in atomic Ni and $s\ensuremath{-}d$ interconfigurational energies of transition elements are almost unchanged by SIC. We also discuss the admissibility of fractional occupation numbers, and present a parametrization of the electron-gas correlation energy at any density, based on the recent results of Ceperley and Alder.
16,027 citations
TL;DR: An exact stochastic simulation of the Schroedinger equation for charged Bosons and Fermions was used to calculate the correlation energies, to locate the transitions to their respective crystal phases at zero temperature within 10%, and to establish the stability at intermediate densities of a ferromagnetic fluid of electrons.
Abstract: An exact stochastic simulation of the Schroedinger equation for charged Bosons and Fermions was used to calculate the correlation energies, to locate the transitions to their respective crystal phases at zero temperature within 10%, and to establish the stability at intermediate densities of a ferromagnetic fluid of electrons.
10,743 citations
Journal Article•
TL;DR: The results of the election were reported by the National Resource for Computing in Chemistry (NCI) as discussed by the authors, a non-profit organization for information technology in the chemical industry, which is based at the Berkeley Lab.
Abstract: ., • ' % . ^ : K ~* B J£L~i0813_ 4JC-4 J NATIONAL RESOURCE FOR COMPUTATION IN CHEMISTRY^ '• • ' THE 81R0UND STATED 6|/THE ELECTION A - - .A r >'--H .1 ,4- v c ' M \>~ r tAWRfctftE BERKELEY LABORATORY «r National
9,385 citations
TL;DR: The basics of the suject are looked at, a brief review of the theory is given, examining the strengths and weaknesses of its implementation, and some of the ways simulators approach problems are illustrated through a small case study.
Abstract: First-principles simulation, meaning density-functional theory calculations with plane waves and pseudopotentials, has become a prized technique in condensed-matter theory. Here I look at the basics of the suject, give a brief review of the theory, examining the strengths and weaknesses of its implementation, and illustrating some of the ways simulators approach problems through a small case study. I also discuss why and how modern software design methods have been used in writing a completely new modular version of the CASTEP code.
9,350 citations