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arXiv 2302.09963cond-mat.mtrl-sci
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负热膨胀材料Cd(CN)$_2$在静水压力下的结构与动力学

Structure and dynamics of the negative thermal expansion material Cd(CN)$_2$ under hydrostatic pressure

University of Oxford(牛津大学);University College London(伦敦大学学院);ETH Zürich(苏黎世联邦理工学院);University of Birmingham(伯明翰大学);Rutherford Appleton Laboratory, STFC(拉瑟福·阿普尔顿实验室,STFC);University of St Andrews(圣安德鲁斯大学)

Chloe S. Coates, Mia Baise, Johanthan M. Bulled, Emma H. Wolpert, Joshua W. Makepeace, Helen C. Walker, Alexandra S. Gibbs, A. Dominic Fortes, Ben Slater, Andrew L. Goodwin

AI总结:

该研究通过中子衍射、非弹性散射和量子化学计算,揭示了Cd(CN)$_2$在压力下的热硬化效应、高压相及声子软化,并发现弹性行为与局部配位环境相关。

摘要:

我们结合变温/变压中子粉末衍射、变压非弹性中子散射和量子化学计算,研究了负热膨胀(NTE)材料$^{114}$Cd(CN)$_2$在静水压力下的行为。我们确定了环境压力相的态方程,并发现了所谓的“热硬化”效应,即材料在加热时弹性变硬。我们还识别了多个高压相,并绘制了Cd(CN)$_2$在$0\leq p\leq0.5$ GPa、$100\leq T\leq300$ K范围内的相行为图。正如对NTE材料所预期的那样,低能声子频率在压力下软化,我们确定了这些模式的有效Grüneisen参数。最后,我们表明Cd(CN)$_2$的弹性行为对局部Cd配位环境敏感,这暗示了Cd(CN)$_2$中短时间尺度(声子)和长时间尺度(氰基翻转)涨落之间的相互作用。

英文摘要:

We use a combination of variable-temperature / variable-pressure neutron powder diffraction, variable-pressure inelastic neutron scattering, and quantum chemical calculations to interrogate the behaviour of the negative thermal expansion (NTE) material $^{114}$Cd(CN)$_2$ under hydrostatic pressure. We determine the equation of state of the ambient-pressure phase, and discover the so-called `warm hardening' effect whereby the material becomes elastically stiffer as it is heated. We also identify a number of high-pressure phases, and map out the phase behaviour of Cd(CN)$_2$ over the range $0\leq p\leq0.5$\,GPa, $100\leq T\leq300$\,K. As expected for an NTE material, the low-energy phonon frequencies are found to soften under pressure, and we determine an effective Gr{ü}neisen parameter for these modes. Finally, we show that the elastic behaviour of Cd(CN)$_2$ is sensitive to the local Cd coordination environment, which suggests an interplay between short- (phononic) and long-timescale (cyanide flips) fluctuations in Cd(CN)$_2$.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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