Nucleating a Different Coordination in a Crystal under Pressure: A Study of the B1-B2 Transition in NaCl by Metadynamics

Here we propose an NPT metadynamics simulation scheme for pressure-induced structural phase transitions, using coordination number and volume as collective variables, and apply it to the reconstructive structural transformation B1-B2 in NaCl. By studying systems with size up to 64 000 atoms we reach a regime beyond collective mechanism and observe transformations proceeding via nucleation and growth. We also reveal the crossover of the transition mechanism from Buerger-like for smaller systems to Watanabe-Toledano for larger ones. The scheme is likely to be applicable to a broader class of pressure-induced structural transitions, allowing study of complex nucleation effects and bringing simulations closer to realistic conditions.

Automated summary

The proposed NPT metadynamics simulation scheme allows studying pressure-induced structural phase transitions beyond the collective mechanism. By using coordination number and volume as collective variables, the scheme can observe transformations proceeding via nucleation and growth, revealing different transition mechanisms for smaller vs. larger systems. This approach is likely applicable to a broader class of pressure-induced structural transitions, enabling study of complex nucleation effects and bringing simulations closer to realistic conditions.