Trudu Federica, Donadio Davide, Parrinello Michele
ETH Zurich, Department of Chemistry and Applied Biosciences, c/o USI-Campus, via Giuseppe Buffi 13, CH-6900 Lugano, Switzerland.
Phys Rev Lett. 2006 Sep 8;97(10):105701. doi: 10.1103/PhysRevLett.97.105701. Epub 2006 Sep 6.
Using molecular dynamics, we investigate the crystal nucleation in a Lennard-Jones fluid as a function of the degree of supercooling. At moderate supercooling, a nucleation picture applies, while for deeper quenches, the phenomenon progressively acquires a spinodal character. We show that in the nucleation regime, the freezing is a two-step process. The formation of the critical nucleus is indeed preceded by the abrupt formation of a precritical crystallite from a density fluctuation in the fluid. In contrast, as the degree of supercooling is increased, crystallization proceeds in a more continuous and collective fashion and becomes more spatially diffuse, indicating that the liquid is unstable and crystallizes by a spinodal mechanism.
利用分子动力学，我们研究了 Lennard-Jones 流体中的晶体成核作为过冷度的函数。在适度过冷时，成核图像适用，而对于更深的骤冷，该现象逐渐呈现出旋节线特征。我们表明，在成核区域，凝固是一个两步过程。临界核的形成确实之前会从流体中的密度涨落突然形成一个亚临界微晶。相比之下，随着过冷度的增加，结晶以更连续和集体的方式进行，并且在空间上变得更加弥散，这表明液体是不稳定的，并通过旋节线机制结晶。
