Kinetic Phase Diagram for Nucleation and Growth of Competing Crystal Polymorphs in Charged Colloids

We determine the kinetic phase diagram for nucleation and growth of crystal phases in a suspension of charged colloids. Exploiting the seeding approach in extensive simulations, we calculate nucleation barrier heights for face-centered cubic (fcc) and body-centered cubic (bcc) phases for varying screening lengths and supersaturations. We determine for the entire metastable fluid region the crystal polymorph with the lowest nucleation barrier, and find a regime close to the triple point where metastable bcc can form due to a lower nucleation barrier, even though fcc is the stable phase. For higher supersaturation, we find that the difference in barrier heights decreases and we observe a mix of hexagonal close-packed, fcc, and bcc structures in the growth of crystalline seeds as well as in spontaneously formed crystals. Our kinetic phase diagram rationalizes the different crystallization mechanisms observed in previous work.

Automated summary

In this study, we determined the kinetic phase diagram for nucleation and growth of crystal phases in a suspension of charged colloids. Our simulations show that the nucleation barrier heights for different crystal phases vary with screening lengths and supersaturations. We found that the crystal polymorph with the lowest nucleation barrier occurs in the entire metastable fluid region, and even though fcc is the stable phase, bcc can form due to a lower nucleation barrier close to the triple point. Additionally, at higher supersaturation, we observed a mix of different crystal structures in both the growth of crystalline seeds and spontaneously formed crystals.