标题： 改性氧化物玻璃中的热导率由模态相变控制 显示英文标题

标题： Thermal conductivity in modified oxide glasses is governed by modal phase changes

摘要： 玻璃的热导率众所周知比晶体材料更难以从理论上描述。 由于这一事实，当超越简单玻璃的情况，例如非晶态SiO$_2$，进入所谓的“改性”氧化物玻璃时，即其他氧化物（例如碱金属氧化物）被加入以破坏网络并改变例如弹性及热性能，对玻璃中热导率的基本理解仍然非常有限。 尽管如此，改性玻璃构成了已知玻璃的大部分，这种知识的缺乏依然明显。 在本研究中，我们研究了一系列表征性的钠硅酸盐（$x\text{Na}_2\text{O}\text{-}(100\text{-}x)\text{SiO}_2$）玻璃。 模态贡献的分析揭示了随着Na$_2$O含量的增加，振动局域化程度增加，振动变得无序，以及模态贡献到热导率的整体减少。 我们发现钠的振动相（声学与光学）相比构成网络的硅和氧物种来说相对无序，这解释了为什么增加Na$_2$O含量会降低热导率。 我们的工作为玻璃热传导的基础以及玻璃中热传导与模态特性之间的相互作用提供了新的见解。 显示英文摘要

摘要： The thermal conductivity of glasses is well-known to be significantly harder to theoretically describe compared to crystalline materials. Because of this fact, the fundamental understanding of thermal conductivity in glasses remain extremely poor when moving beyond the case of simple glasses, e.g., glassy SiO$_2$, and into so-called 'modified' oxide glasses, that is, glasses where other oxides (e.g. alkali oxides) have been added to break up the network and alter e.g. elastic and thermal properties. This lack of knowledge is apparent despite how modified glasses comprise the far majority of known glasses. In the present work we study an archetypical series of sodium silicate ($x\text{Na}_2\text{O}\text{-}(100\text{-}x)\text{SiO}_2$) glasses. Analyses of modal contributions reveal how increasing Na$_2$O content induces increasing vibrational localization with a change of vibrations to be less ordered, and a related general decrease in modal contributions to thermal conductivity. We find the vibrational phases (acoustic vs. optical) of sodium vibrations to be relatively disordered compared to the network-forming silicon and oxygen species, explaining how increasing Na$_2$O content decreases thermal conductivity. Our work sheds new light on the fundamentals of glassy heat transfer as well as the interplay between thermal conduction and modal characteristics in glasses.