Factors influencing thermal solidification of bent-core trimers

Abstract

Bent-core trimers are a simple model system for which the competition between crystallization and glass-formation can be tuned by varying a single parameter:\ the bond angle $θ_0$. Using molecular dynamics simulations, we examine how varying $θ_0$ affects their thermal solidification. By examining trends with $θ_0$, comparing these to trends in trimers' jamming phenomenology, and then focusing on the six $θ_0$ that are commensurable with close-packed crystalline order, we obtain three key results: \textbf{(i)} the increase in trimers' solidification temperature $T_s(θ_0)$ as they straighten (as $θ_0 \to 0^\circ$) is driven by the same gradual loss of \textit{effective} configurational freedom that drives athermal trimers' decreasing $ϕ_J(θ_0)$; \textbf{(ii)} $θ_0$ that allow formation of both FCC and HCP order crystallize, while $θ_0$ that only allow formation of HCP order glass-form; \textbf{(iii)} local cluster-level structure at temperatures slightly \textit{above} $T_s(θ_0)$ is highly predictive of whether trimers will crystallize or glass-form.