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Theoretical assessment on the possibility of constraining point-defect energetics by pseudo phase transition pressures

机译：拟相变压力约束点缺陷能量的可能性的理论评估

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Making use of the energetics and equations of state of defective uranium dioxide that are calculated with first-principles methods, we demonstrate the possibility of constraining the formation energy of point defects by measuring the transition pressures of the corresponding pseudo phase of defects. The mechanically stable range of fluorite structure of UO_2, which dictates the maximum possible pressure of relevant pseudo phase transitions, gives rise to defect formation energies that span a wide band and overlap with the existing experimental estimates. We reveal that the knowledge about pseudo phase boundaries can not only provide important information on energetics that is helpful for reducing the scattering in current estimates, but also be valuable for guiding theoretical assessments, even to validate or disprove a theory. In order to take defect interactions into account and to extrapolate the physical quantities at finite stoichiometry deviations to that near the stoichiometry, we develop a general formalism to describe the thermodynamics of a defective system. We also show that it is possible to include interactions among defects in a simple expression of a point defect model (PDM) by introducing an auxiliary constant mean field. This generalization of the simple PDM leads to great versatility that allows one to study nonlinear effects of stoichiometry deviation on materials' behavior. It is a powerful tool to extract the defect energetics from finite defect concentrations to the dilute limit. Besides these, the full content of the theoretical formalism and some relevant and interesting issues, including reentrant pseudo transition, multiple-defect coexistence, charged defects, and possible consequence of instantaneous defective response in a quantum crystal, are explored and discussed.
机译：利用通过第一性原理方法计算出的有缺陷的二氧化铀的能量和状态方程，我们证明了通过测量缺陷的相应伪相的转变压力来限制点缺陷的形成能的可能性。 UO_2的萤石结构的机械稳定范围决定了相关假相变的最大可能压力，从而产生了跨越宽带且与现有实验估计重叠的缺陷形成能。我们揭示，关于伪相位边界的知识不仅可以提供有关能量学的重要信息，有助于减少当前估计中的散射，而且对于指导理论评估甚至验证或反证理论都具有宝贵的价值。为了考虑缺陷的相互作用并将有限的化学计量偏差下的物理量外推到接近化学计量的物理量，我们开发了一种通用形式主义来描述缺陷系统的热力学。我们还表明，通过引入辅助常数平均场，可以在点缺陷模型（PDM）的简单表达式中包括缺陷之间的相互作用。简单PDM的这种泛化导致了极大的多功能性，使人们能够研究化学计量偏差对材料性能的非线性影响。它是从有限的缺陷浓度到稀释极限中提取缺陷能量的有力工具。除此之外，还探讨和讨论了理论形式主义的全部内容以及一些相关和有趣的问题，包括折返伪过渡，多缺陷共存，带电缺陷以及量子晶体中瞬时缺陷响应的可能后果。

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  • 来源
    《Physical review》 |2013年第17期|48-60|共13页
  • 作者

    Hua Y. Geng; Hong X. Song; Q. Wu;

  • 作者单位

    National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, CAEP, P.O. Box 919-102 Mianyang, Sichuan 621900, People's Republic of China;

    National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, CAEP, P.O. Box 919-102 Mianyang, Sichuan 621900, People's Republic of China;

    National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, CAEP, P.O. Box 919-102 Mianyang, Sichuan 621900, People's Republic of China;

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