铀的结构相变及力学性能的第一性原理计算*
First principles studies of phase transition and mechanical properties of uranium
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摘要: 基于密度泛函理论,分别计算了α,γ铀的晶格常数、平衡态体积、体弹模量及其导数等,与实验和其他第一性原理计算结果符合较好;并根据焓-压强曲线得到了两相的相变压强~111 GPa.通过体心立方结构理想拉伸强度的计算,分析其在极端加载条件下的结构行为.另外,计算了小应变情况下U-Nb (6.25 at.%)的能量-应变关系,发现对应于剪切模量c′的应变会使得该结构的能量降低,揭示了该结构的力学不稳定性.Abstract: Using density functional theory, the structural parameters ofα-U and bcc phases were obtained separately, in reasonable agree-ment with previous experimental and theoretical results. The enthalpy-pressure curve showed that the phase transition pressure was approximately 111 GPa. The structural behavior ofγ-U under extreme loading conditions was exhibited by the ideal strength calcu-lations. In addition, by analyzing the energy-strain relationship we found that the strain corresponding to the shear modulus c′could decrease the total energy of U-Nb (6.25 at.%) alloy, indicating the instability of this structure.
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