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A Calculation Approach to Elastic Constants of Crystallines at High Pressure and Finite Temperature 下载免费PDF全文
Elastic constants of Na and Li metals are calculated successfully for temperatures up to 350K and pressures up to 30GPa using a scheme without involving any adjustable parameter.Elastic constants are assumed to depend only on an effective pair potential that is only determined by the average interatomic distance.Temperature has an effect on elastic constants by way of charging the equilibrium.The elastic constants can be obtained by fitting the relationship between total energy and strain tensor using the new set of lattice parameters obtained by calculating displacement of atoms at the finite temperature and at a fixed pressure.The relationship between the effective pair potential and the interatiomic distance is fitted by using a series of data of cohesive energy corresponding to lattice parameters. 相似文献
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The relation between particle velocity Up, up to 4 km/s, and shock wave velocity Us in copper has been simulated with ab initio molecular dynamics. The simulated relationship without considering the correction of zero-point and finite temperature effects is Us = 4.23 1.53Up. After considering the correction the relation becomes Us = 4.08 1.53Up, which is consistent with the experimental result. 相似文献
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As a widely used pressure calibrator, the structural phase transitions of bismuth from phase I, to phase II, to phase III,and then to phase V with increasing pressure at 300 K have been widely confirmed. However, there are different structural versions for phase III, most of which are determined by x-ray diffraction(XRD) technology. Using x-ray absorption fine structure(XAFS) measurements combined with ab initio calculations, we show that the proposed incommensurate composite structure of bismuth of the three configurations is the best option. An abnormal continuous increase of the nearest-neighbor distance of phase III with elevated pressure is also observed. The electronic structure transformation from semimetal to metal is responsible for the complex behavior of structure transformation. 相似文献
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The equation of state of face-centred-cubic (fcc) copper crystals at pressures up to 500 GPa and relative volume to 0.55 have been evaluated by using the full-potential linear muffin-tin orbital (FPLMTO) total-energy method combining with a mean-field model of the vibrational partition function. The mean-field is constructed from the sum of all the pair potentials between the reference atom and the others of the system. The calculated properties are in good agreement with the available shock-wave experimental measurements. 相似文献
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Xiaobing Fan 《中国物理 B》2022,31(5):56101-056101
It is unclear whether there is a liquid-liquid phase transition or not in the bismuth melt at high temperature and high pressure. If so, it will be necessary to confirm the boundary of the liquid-liquid phase transition and clarify whether it is a first-order phase transition. Here, based on x-ray absorption spectra and simulations, the temperature dependence of bismuth structures is investigated under different pressures. According to the similarity of characteristic peaks of x-ray absorption near edge structure (XANES) spectra, we estimate the possible temperature ranges of liquid-liquid phase transition to be 779-799 K at 2.74 GPa and 859-879 K at 2.78 GPa, 809-819 K at 3.38 GPa and 829-839 K at 3.39 GPa and 729-739 K at 4.78 GPa. Using ab initio molecular dynamics (AIMD) simulations, we obtain the stable structures of the bismuth melt at different temperatures and pressures, and calculated their electronic structures. Meanwhile, two stable phases (phase III-like and phase IV-like) of bismuth melts are obtained from different initial phases of bismuth solids (phase III and phase IV) under the same condition (3.20 GPa and 800 K). Assuming that the bismuth melt undergoes a phase transition from IV-like to III-like between 809 K and 819 K at 3.38 GPa, the calculated electronic structures are consistent with the XANES spectra, which provides a possible explanation for the first-order liquid-liquid phase transition. 相似文献
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状态方程与描述能量、动量、质量守恒的偏微分方程一起,构成了可求解材料动态压缩行为的完备流体力学方程组。动态压缩下,相变会导致材料内能、密度、强度等物理性质的不连续变化,需要构建多相状态方程模型才能精确描述这些变化。通过多相状态方程模型的自动组装,采用计算机智能优化算法自动校准状态方程模型参数,发展了自动化的多相状态方程建模程序AEOS(automated equation of state)。利用AEOS,构建了锡的3套状态方程模型,3套模型的计算结果与相关实验结果基本一致,验证了AEOS程序的适用性。将构建的状态方程模型应用于一维流体力学模拟,发现锡冲击到17 GPa再等熵卸载到常压的压力-温度路径会经过β相-体心四方相-液相三相点,并且可以很好地解释在15.4 GPa的冲击压力下锡的微喷颗粒呈现固-液混合态的实验现象。AEOS的良好表现证明其在大型数字化科研平台以及高通量材料物性计算中将具有广泛的应用前景。 相似文献
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用二级氢气炮作为冲击压缩加载工具和多通道瞬态辐射高温计作为主要测量系统,测量了冲击压缩氦气等离子体的光辐亮度历史(初始温度293K,初始压力为1.2MPa)。根据实测记录信号波形的有关特征量,计算得到了氦等离子体的Hugoniot物态方程(含冲击温度)。结果发现:实测Hugoniot物态方程可用Saha方程加Debye-Huckel修正物理模型解释。 相似文献