Diamond precipitation in warm dense titanium carbide*

Carbon precipitation forming diamond has been observed in compressed hydrocarbon and carbide materials, mimicking the conditions in planetary interiors. The materials serving as carbon sources display a wide-ranging set of physical and chemical characteristics – from covalently bonded hydrocarbons to metallic carbides – which hint at diverse pathways to diamond precipitation. Inspired by recent work [1] on dense hydrocarbon mixtures which determined necessary conditions for diamond formation, we use first-principles density functional calculations to investigate the mechanism of diamond formation in compressed titanium carbide.

We construct a series of Ti-C convex hulls from ambient to multi-megabar pressures to explore the structural features which occur in dense Ti-C mixtures, focusing on diamond-like motifs arising in binary phases [2]. These are extended to finite-temperature conditions to examine the evolution of phase stability. Ab initio molecular dynamics simulations are used to situate the diamond formation process around the system melting behavior and to track the atomic-level process of diamond nucleation and growth. The goal is to provide a complete picture on the diamond precipitation mechanism in ramp-compressed warm and dense TiC. 

[1] Cheng, B. et al., Nat. Commun. 14, 1104 (2023)

[2] Chunhong, X. et al., RSC Adv. 8, 14479 (2018)