In the scientific report “Metastability and Ostwald step rule in the crystallisation of diamond and graphite from molten carbon” published in Nature Communications, researchers from George Washington University and the University of California, Davis (UC Davis) shed light on the crystallisation kinetics of diamond and graphite, which is critical for melting and recrystallisation experiments. From GW Engineering’s Department of Civil and Environmental Engineering, Professor Tianshu Li, doctoral student Wanyu Zhao, and Research Scientist Shunda Chen contributed to the study.
Here is an excerpt from the study abstract: “Here, we reveal the microscopic mechanisms of diamond and graphite nucleation from liquid carbon through molecular simulations with first-principles machine learning potentials. Our simulations accurately reproduce the experimental phase diagram of carbon near the triple point and show that liquid carbon crystallises spontaneously upon cooling."
Read the full study in the journal Nature Communications. For a summary of the study's most significant findings, check out this UC Davis article, "Molecular Simulations Show Graphite 'Hijacks' Diamond Formation Through Unexpected Crystallization Pathways."
In the follow-up piece by Physics World, “Graphite ‘hijacks’ the journey from molten carbon to diamond,” the researchers discuss why molten carbon “chooses” to crystallize into diamond or graphite, which Li shares is because of Ostwald’s step rule.
Here is an excerpt from the article: “The liquid carbon essentially finds it easier to become graphite first, even though diamond is ultimately more stable under these conditions,” says co-author Tianshu Li, a professor of civil and environmental engineering at George Washington University. “It’s nature taking the path of least resistance.”
Read the full article on Physics World.