Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2010 Jun 11;104(23):235502. doi: 10.1103/PhysRevLett.104.235502.
At low temperatures silicon is a brittle material that shatters catastrophically, whereas at elevated temperatures, the behavior of silicon changes drastically over a narrow temperature range and suddenly becomes ductile. This brittle-to-ductile transition has been observed in experimental studies, yet its fundamental mechanisms remain unknown. Here we report an atomistic-level study of a fundamental event in this transition, the change from brittle cleavage fracture to dislocation emission at crack tips, using the first principles based reactive force field. By solely raising the temperature, we observe an abrupt change from brittle cracking to dislocation emission from a crack within a ≈10 K temperature interval.
在低温下，硅是一种易碎材料，会灾难性地破碎，而在高温下，硅的行为在很窄的温度范围内发生剧烈变化，突然变得具有延展性。这种从脆性到韧性的转变已经在实验研究中观察到，但它的基本机制仍然未知。在这里，我们使用基于第一性原理的反应力场，对该转变中的一个基本事件进行了原子级研究，即从脆性的解理断裂到裂纹尖端的位错发射的转变。仅通过提高温度，我们就在大约 10 K 的温度间隔内观察到了从脆性开裂到裂纹内位错发射的突然转变。
