Wang Lei, Wang Cong, Chen Ying
Department of Physics, University of Science and Technology Beijing, Beijing 100083, People's Republic of China.
J Phys Condens Matter. 2019 Nov 20;31(46):465003. doi: 10.1088/1361-648X/ab3673. Epub 2019 Jul 29.
Positive expansion on heating, and positive contraction on hydrostatic compression are our general understanding. Actually, the abnormal negative thermal expansion (NTE) or negative linear compressibility (NLC) behavior is permissible, but exists in very few materials. Interestingly, we find that the NTE and NLC behaviors can coexist in the low-dimensional black phosphorene using first-principles calculations. In the temperature-field, the volume-NTE of black phosphorene can be exhibited below about 200 K, while the axial-NTE exists in the whole studied temperature range. In the hydrostatic pressure-field, the NLC behavior can occur along a zigzag direction or armchair direction in different pressure ranges. The phonon abnormality in black phosphorene is detected. It is found that acoustic phonons, especially the lowest-frequency TA mode, play a very important role. The re-entrant honeycomb network in black phosphorene, as the specific topology, will facilitate the occurrence of NTE and NLC behaviors. This work can provide some foundations and clues for exploring the abnormal properties in other 2D materials.
我们通常的理解是，材料加热时会发生正膨胀，静水压缩时会发生正收缩。实际上，异常的负热膨胀（NTE）或负线性压缩率（NLC）行为是可能存在的，但只存在于极少数材料中。有趣的是，我们通过第一性原理计算发现，低维黑磷烯中NTE和NLC行为可以共存。在温度场中，黑磷烯的体积NTE在约200 K以下会出现，而轴向NTE则存在于整个研究温度范围内。在静水压力场中，NLC行为会在不同压力范围内沿锯齿方向或扶手椅方向出现。检测到黑磷烯中的声子异常。发现声学声子，尤其是最低频率的TA模式，起着非常重要的作用。黑磷烯中重入式蜂窝网络作为特定的拓扑结构，将促进NTE和NLC行为的发生。这项工作可为探索其他二维材料的异常性质提供一些基础和线索。
