Lone pair electrons minimize lattice thermal conductivity
Lone pair electrons minimize lattice thermal conductivity
复制标题
DOI：
10.1039/c2ee23391f
复制
发表时间：
2013-02-01
影响因子：
32.5
通讯作者：
Heremans, Joseph P.
中科院分区：
文献类型：
--
作者：
Nielsen, Michele D.;Ozolins, Vidvuds;Heremans, Joseph P.
由于世界上93%以上的能源来自热过程，因此最大限度地提高热传递或最大限度地减少热浪费的新材料对于提高效率至关重要。在这里，我们专注于完全致密的电绝缘体在低端的晶格热导率k（L）的频谱。我们提出了一个实验验证的预测工具，显示孤对电子电荷密度的高变形性如何限制晶体材料中的k（L）。利用第一性原理密度泛函理论（DFT）计算，我们预测了几种ABX（2）（Ⅰ-Ⅴ-Ⅵ 2族）岩盐结构化合物由于Ⅴ族阳离子的孤对电子与Ⅵ族阴离子的价p轨道之间的强杂化和排斥作用，将产生软声子模.在许多情况下，这会导致晶格不稳定，化合物要么不存在，要么以不同的结构结晶。边缘稳定的ABX（2）化合物具有非谐键，导致强的声子-声子相互作用。我们的实验表明，这些可以减少k（L）的非晶极限。
As over 93% of the world's energy comes from thermal processes, new materials that maximize heat transfer or minimize heat waste are crucial to improving efficiency. Here we focus on fully dense electrical insulators at the low end of the spectrum of lattice thermal conductivity k(L). We present an experimentally validated predictive tool that shows how the high deformability of lone-pair electron charge density can limit k(L) in crystalline materials. Using first-principles density-functional theory (DFT) calculations, we predict that several ABX(2) (groups I-V-VI2) compounds based on the rocksalt structure develop soft phonon modes due to the strong hybridization and repulsion between the lone-pair electrons of the group V cations and the valence p orbitals of group VI anions. In many cases, this creates lattice instabilities and the compounds either do not exist or crystallize in a different structure. Marginally stable ABX(2) compounds have anharmonic bonds that result in strong phonon-phonon interactions. We show experimentally how these can reduce k(L) to the amorphous limit.