Polymorph selection during the crystallization of softly repulsive spheres: the inverse power law potential.
Polymorph selection during the crystallization of softly repulsive spheres: the inverse power law potential.
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DOI：
10.1021/jp0753023
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发表时间：
2007-10
期刊：
影响因子：
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通讯作者：
C. Desgranges;J. Delhommelle
中科院分区：
文献类型：
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作者：
C. Desgranges;J. Delhommelle
使用混合蒙特卡罗分子模拟，我们研究了通过反幂律势相互作用的软排斥球体熔化的结晶。我们在固定过冷度下工作（即温度低于熔化温度 25%），并考虑由不同的反幂指数 n 值定义的三个系统：n = 5、n = 6.67 和 n = 10。修改 n 的值使我们能够研究体心立方 (bcc) 相（n = 5 和 n = 6.67）稳定域中的结晶开始。面心立方 (fcc) 相的稳定性 (n = 10)。我们表明，对于这三个系统，在晶体成核过程中不会发生多晶型选择，因为这三个系统获得的临界核的结构尚未明确定义。然而，我们的结果表明，多晶型选择发生在生长步骤中，因为对于两个较小的 n 值（n = 5 和 n = 6.67），生长要么进入稳定的 bcc 相，要么对于较大的 n 值（n = 10）进入稳定的 fcc 相。我们还表明，对于 n = 10，我们没有实现对多晶型的完全控制。生长步骤要么产生由不同结构的两个块（稳定的 fcc 形式和亚稳态 bcc 形式）组成的缓慢生长的微晶，要么产生快速生长的亚稳态 bcc 形式的微晶。
Using hybrid Monte Carlo molecular simulations, we study crystallization from the melt of softly repulsive spheres interacting through an inverse power law potential. We work at fixed supercooling (i.e., at a temperature 25% below the melting temperature) and consider three systems, defined by different values for the inverse power exponent n: n = 5, n = 6.67, and n = 10. Modifying the value of n allows us to study the onset of crystallization in the domain of stability of the body-centered cubic (bcc) phase (n = 5 and n = 6.67) and in the domain of stability of the face-centered cubic (fcc) phase (n = 10). We show that, for the three systems, polymorph selection does not take place during crystal nucleation since the structure of the critical nuclei obtained for the three systems is not well defined. However, our results demonstrate that polymorph selection takes place during the growth step since growth proceeds either into the stable bcc phase for the two smaller values of n (n = 5 and n = 6.67) or into the stable fcc phase for the larger value of n (n = 10). We also show that we did not achieve complete control of polymorphism for n = 10. The growth step gives rise to either slowly growing crystallites composed of two blocks of different structures (the stable fcc form and the metastable bcc form) or rapidly growing crystallites of the metastable bcc form.