文章基本信息

标题：Anomalous dynamics of interstitial dopants in soft crystals
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作者：Justin Tauber ; Ruben Higler ; Joris Sprakel 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：48
页码：13660-13665
DOI：10.1073/pnas.1609595113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceDoping crystalline solids with small impurity atoms is a common approach to tailor material properties, for example to increase mechanical toughness in making steel or to create solid-state batteries. The properties and longevity of doped materials depend sensitively on the spatial distribution and dynamics of the dopants within the lattice. In this paper we show how classical approaches to predict dopant dynamics fail in crystals approaching their melting point. Thermal excitation of the, on-average perfect, lattice breaks local inversion symmetry, causing an instantaneous disordered potential field. As a consequence, the dopants exhibit anomalous and heterogeneous dynamics within an ordered solid. This result sheds unique light on the complex behavior of doped materials that cannot be explained using classical lattice theories. The dynamics of interstitial dopants govern the properties of a wide variety of doped crystalline materials. To describe the hopping dynamics of such interstitial impurities, classical approaches often assume that dopant particles do not interact and travel through a static potential energy landscape. Here we show, using computer simulations, how these assumptions and the resulting predictions from classical Eyring-type theories break down in entropically stabilized body-centered cubic (BCC) crystals due to the thermal excitations of the crystalline matrix. Deviations are particularly severe close to melting where the lattice becomes weak and dopant dynamics exhibit strongly localized and heterogeneous dynamics. We attribute these anomalies to the failure of both assumptions underlying the classical description: (i) The instantaneous potential field experienced by dopants becomes largely disordered due to thermal fluctuations and (ii) elastic interactions cause strong dopant-dopant interactions even at low doping fractions. These results illustrate how describing nonclassical dopant dynamics requires taking the effective disordered potential energy landscape of strongly excited crystals and dopant-dopant interactions into account.
关键词：anomalous dynamics ; doping ; crystals