Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, CA 94550 USA. Program in Applied and Computational Mathematics, Princeton University, Princeton, NJ 08544, USA.
Department of Chemistry, New York University (NYU), New York, NY 10003, USA. Courant Institute of Mathematical Sciences, NYU, New York, NY 10012, USA. NYU-East China Normal University Center for Computational Chemistry at NYU Shanghai, Shanghai 200062, China.
Science. 2014 Nov 7;346(6210):729-32. doi: 10.1126/science.1253810.
The melting of a solid, like other first-order phase transitions, exhibits an intrinsic time-scale disparity: The time spent by the system in metastable states is orders of magnitude longer than the transition times between the states. Using rare-event sampling techniques, we find that melting of representative solids-here, copper and aluminum-occurs via multiple, competing pathways involving the formation and migration of point defects or dislocations. Each path is characterized by multiple barrier-crossing events arising from multiple metastable states within the solid basin. At temperatures approaching superheating, melting becomes a single barrier-crossing process, and at the limit of superheating, the melting mechanism is driven by a vibrational instability. Our findings reveal the importance of nonlocal behavior, suggesting a revision of the perspective of classical nucleation theory.
固体的熔化像其他一级相变一样，表现出内在的时间尺度差异：系统在亚稳态下花费的时间比状态之间的转变时间长几个数量级。使用稀有事件抽样技术，我们发现代表性固体（这里是铜和铝）的熔化是通过多种竞争途径发生的，涉及点缺陷或位错的形成和迁移。每条路径的特征是多个跨越多个亚稳态的势垒的事件。在接近过热的温度下，熔化成为单一的势垒跨越过程，而在过热的极限下，熔化机制由振动不稳定性驱动。我们的发现揭示了非局部行为的重要性，这表明需要对经典成核理论的观点进行修正。
