THERMAL-EXPANSION AND X-RAY-ABSORPTION FINE-STRUCTURE CUMULANTS

被引:228
作者
FRENKEL, AI [1 ]
REHR, JJ [1 ]
机构
[1] UNIV WASHINGTON,DEPT PHYS,SEATTLE,WA 98195
来源
PHYSICAL REVIEW B | 1993年 / 48卷 / 01期
关键词
D O I
10.1103/PhysRevB.48.585
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
In the classical limit, a simple relation has been shown to exist between the thermal expansion coefficient a and the cumulants of the vibrational amplitude that axe measured in x-ray-absorption fine structure (XAFS), i.e., alpharTsigma2/sigma(3) = 1/2, where sigma2 is the mean-square vibrational amplitude, sigma(3) the third cumulant, T the absolute temperature, and r the equilibrium bond length. We generalize this relation to the quantum case using a correlated Einstein model and thermodynamic perturbation theory, and find alpharTsimga2/sigma(3) = [3z(1 + z)ln(1/z)]/[(1 - z)(1 + 10z + z2)], where z = exp(-THETA(E)/T), and THETA(E) is the Einstein temperature. This result is found to be in agreement with the measured thermal expansion coefficient and XAFS cumulants in RbBr at 30 K and 125 K.
引用
收藏
页码:585 / 588
页数:4
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