Buehler Markus J, Tang Harvey, van Duin Adri C T, Goddard William A
Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 1-272, Cambridge, MA 02139, USA.
Phys Rev Lett. 2007 Oct 19;99(16):165502. doi: 10.1103/PhysRevLett.99.165502. Epub 2007 Oct 18.
Fracture experiments of single silicon crystals reveal that after the critical fracture load is reached, the crack speed jumps from zero to approximately 2 km/sec, indicating that crack motion at lower speeds is forbidden. This contradicts classical continuum fracture theories predicting a continuously increasing crack speed with increasing load. Here we show that this threshold crack speed may be due to a localized phase transformation of the silicon lattice from 6-membered rings to a 5-7 double ring at the crack tip.
单晶硅的断裂实验表明，在达到临界断裂载荷后，裂纹速度从零跃升至约2千米/秒，这表明较低速度下的裂纹运动是被禁止的。这与经典连续介质断裂理论相矛盾，该理论预测裂纹速度会随着载荷增加而持续增加。在此我们表明，这种临界裂纹速度可能是由于裂纹尖端硅晶格从六元环局部转变为5-7双环所致。
