State Key Laboratory of Silicon Materials and Center of Electron Microscopy, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China.
State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences (CAS), Shanghai, 200050, P. R. China.
Adv Mater. 2019 Jan;31(4):e1804919. doi: 10.1002/adma.201804919. Epub 2018 Nov 13.
Phase transition is a fundamental physical phenomenon that has been widely studied both theoretically and experimentally. According to the Landau theory, the coexistence of high- and low-temperature phases is thermodynamically impossible during a second-order phase transition in a bulk single crystal. Here, the coexistence of two (α and β) phases in wedge-shaped nanosized single-crystal Cu Se over a large temperature range are demonstrated. By considering the surface free-energy difference between the two phases and the shape effect, a thermodynamic model is established, which explicitly explains their coexistence. Intriguingly, it is found that with a precise control of the heating temperature, the phase boundary can be manipulated at atomic level. These discoveries extend the understanding of phase transitions to the nanoscale and shed light on rational manipulation of phase transitions in nanomaterials.
相变是一种基本的物理现象，已经在理论和实验上得到了广泛的研究。根据朗道理论，在体单晶的二级相变过程中，高温相和低温相在热力学上是不可能共存的。在这里，我们证明了在较大的温度范围内，楔形纳米单晶 CuSe 中存在两种（α 和 β）相的共存。通过考虑两相之间的表面自由能差和形状效应，建立了一个热力学模型，明确解释了它们的共存。有趣的是，我们发现通过精确控制加热温度，可以在原子水平上操纵相界。这些发现将相变的理解扩展到了纳米尺度，并为在纳米材料中合理操纵相变提供了思路。
