High-temperature behaviour of average structure and vibrational density of states in the ternary superionic compound AgCuSe
High-temperature behaviour of average structure and vibrational density of states in the ternary superionic compound AgCuSe
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DOI：
10.1140/epjb/e2006-00253-3
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发表时间：
2006-06
期刊：
影响因子：
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通讯作者：
D. Trots;A. Skomorokhov;M. Knapp;H. Fuess,
中科院分区：
文献类型：
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作者：
D. Trots;A. Skomorokhov;M. Knapp;H. Fuess,
本文报道了非超离子β-和超离子α-AgCuSe的同时热分析（STA）、同步辐射粉末衍射（300-973 K）和非弹性中子散射（285和505 K）的结果。样品在氩气中加热时稳定。超离子相变时的体积变化约为5%。提出了α-AgCuSe的平均结构模型。平均结构的参数的温度依赖性没有发现异常。α-AgCuSe的离子导电性可能来源于<100 >通过八面体空腔的外围在最近邻四面体位置之间的“偏斜”方向上的阳离子跳跃。提出了α-AgCuSe中阳离子再分布的温度依赖性与离子电导率的温度依赖性之间的关系。温度升高时对声子宽度的各种贡献（非谐效应、时均静态无序和声子-声子散射）导致β-和α-AgCuSe的中子加权态密度发生显著变化，并伴随超离子相变。
Results of simultaneous thermal analysis (STA), synchrotron powder diffraction (in the range 300–973 K) and inelastic neutron scattering (at 285 and 505 K) on non-superionic β- and superionic α-AgCuSe are reported. The sample is stable in argon on heating. The volume change at the superionic phase transition is about 5%. A model for the average structure of α-AgCuSe is proposed. No anomalies in the temperature dependence of the parameters of the average structure were revealed. Ionic conductivity in α-AgCuSe can originate from cation jumps in “skewed” <100 > directions between nearest-neighbour tetrahedral sites via the peripheries of the octahedral cavities. A correlation between the temperature dependence of the cation redistribution in α-AgCuSe and the temperature dependence of the ionic conductivity is supposed. Various contributions (anharmonic effects, time-average static disorder and phonon-phonon scattering) to the widths of individual phonons upon temperature increase lead to pronounced changes in the neutron-weighted densities of states of β- and α-AgCuSe and accompany the superionic phase transition as well.