Origin of the transition entropy in vanadium dioxide
Origin of the transition entropy in vanadium dioxide
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DOI：
10.1103/physrevb.99.064113
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发表时间：
2019-02-26
影响因子：
3.7
通讯作者：
Grau-Crespo, Ricardo
中科院分区：
文献类型：
--
作者：
Mellan, Thomas A.;Wang, Hao;Grau-Crespo, Ricardo
VO 2在T-c接近340 K时的可逆金属-绝缘体转变已经被仔细研究，但其热力学起源仍然不明确。我们讨论了起源的过渡熵的计算电子和声子的贡献，在T-c使用密度泛函理论。的振动频率从谐波声子计算，与软模式，在零温度下的虚重正化到真实的值，在TC使用实验信息从扩散X射线散射在高对称波矢量。高斯过程回归用于推断整个布里渊区的波矢量的变换频率，进而计算有限温度声子配分函数来预测跃迁热力学。使用这种方法，我们预测VO 2的相变是由声子熵超过电子熵驱动的5比1，并预测与量热值一致（在5%以内）的总跃迁熵。
The reversible metal-insulator transition in VO2 at T-c approximate to 340 K has been closely scrutinized yet its thermodynamic origin remains ambiguous. We discuss the origin of the transition entropy by calculating the electron and phonon contributions at T-c using density functional theory. The vibration frequencies are obtained from harmonic phonon calculations, with the soft modes that are imaginary at zero temperature renormalized to real values at T-c using experimental information from diffuse x-ray scattering at high-symmetry wave vectors. Gaussian process regression is used to infer the transformed frequencies for wave vectors across the whole Brillouin zone, and in turn compute the finite temperature phonon partition function to predict transition thermodynamics. Using this method, we predict the phase transition in VO2 is driven 5 to 1 by phonon entropy over electronic entropy, and predict a total transition entropy that agrees (within 5%) with the calorimetric value.