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首页> 外文期刊>Physica, B. Condensed Matter >Ab initio study of phase stability, thermodynamic and elastic properties of C _3N _2 derived from cubic C _(20)
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Ab initio study of phase stability, thermodynamic and elastic properties of C _3N _2 derived from cubic C _(20)

机译:从立方C _(20)衍生的C _3N _2的相稳定性,热力学和弹性性质的从头算研究

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摘要

In this work, we report a quite different conclusion from Tian et al. [Phys. Rev. B 78 (2008) 235431]. It is proved that β-C _3N _2 is the only phase under high pressure, and α-C _3N _2 does not exist. β-C _3N _2 is a covalent crystal composed of strong CC and CN covalent bonds. Band gap of β-C _3N _2 increases with pressure. The width of antibonding state, shown in partial density of states (PDOS), keeps about 5 eV with rising pressures, which brings stable CN or CC covalent bonds. At sufficiently low temperatures, heat capacity (C _v) is proportional to T ~3; and at intermediate temperatures, C _v is governed by the details of vibrations of the atoms; finally, C _v reaches to β-C _3N _2s Dulong-Pettit limit (about 120 J/mol K). Though thermal expansion coefficient (α) increases with temperature, α is less than 1×10 ~(-5) K ~(-1). Elastic constants rise with pressure, but shear moduli is quite steady which increases just a little with pressures.
机译:在这项工作中,我们报告了与Tian等人截然不同的结论。 [物理版本B 78(2008)235431]。证明了β-C_3N _2是高压下唯一的相,而α-C_3N _2不存在。 β-C_3N _2是由强CC和CN共价键组成的共价晶体。 β-C_3N _2的带隙随压力增加。反键态的宽度以状态的部分密度(PDOS)表示,随着压力的升高保持约5 eV,从而带来稳定的CN或CC共价键。在足够低的温度下,热容(C _v)与T〜3成正比;在中间温度下,C _v由原子振动的细节决定;最后,C _v达到β-C_3N _2s Dulong-Pettit极限(约120 J / mol K)。尽管热膨胀系数(α)随着温度增加,但是α小于1×10〜(-5)K〜(-1)。弹性常数随压力而增加,但剪切模量相当稳定,随压力而增加一点。

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