Chemistry-Mediated Ostwald Ripening in Carbon-Rich C/O Systems at Extreme Conditions

Abstract

There is significant interest in establishing a capability for tailored synthesis of next-generation carbon-based nanomaterials due to their broad range of applications and high degree of tunability. High pressure (e.g. shockwave-driven) synthesis holds promise as an effective discovery method, but experimental challenges preclude elucidating the processes governing nanocarbon production from carbon-rich precursors that could otherwise guide efforts through the prohibitively expansive design space. Here we report findings from large scale atomistically-resolved simulations of carbon condensation from C/O mixtures subjected to extreme pressures and temperatures, made possible by machine-learned reactive interatomic potentials. We find that liquid nanocarbon formation follows classical growth kinetics driven by Ostwald ripening (i.e. growth of large clusters at the expense of shrinking small ones) and obeys dynamical scaling in a process mediated by carbon chemistry in the surrounding reactive fluid. The results provide direct insight into carbon condensation in a representative system and pave the way for its exploration in higher complexity organic materials. They also suggest that simulations using machine-learned interatomic potentials could eventually be employed as in-silico design tools for new nanomaterials.

Hierarchical Transfer Learning: An Agile and Equitable Strategy for Machine-Learning Interatomic Models

“…[56][57][58][59] Interactions were described through the Perdew-Burke-Ernzerhof generalized gradient approximation functional, 60,61 projectoraugmented wave pseudopotentials 62,63 (PAW), and the DFT-D2 method 64 for description of dispersion interactions, which has previously been shown to be well suited for describing C and N containing materials under extreme conditions. 35,50,65 All reported calculations were spin-restricted; we note that, consistent with other studies of C, H, O, and N-containing materials shocked to comparable conditions 42,66 spin-restricted and -unrestricted calculations yielded similar results. DFT simulations were run in the canonical ensemble with a 0.5 fs timestep, for 5 ps.…”