The graphite-diamond transition, under high-pressure and high-temperature conditions, has been a central subject in physical science. However, its atomistic mechanism remains under debate. Employing large-scale molecular dynamics (MD) simulations, we report a mechanism whereby the diamond nuclei in the graphite matrix propagate in two preferred directions, among which the graphite [120] is about 2.5 times faster than [001]. Consequently, cubic diamond (CD) is the kinetically favorable product, while only a few hexagonal diamonds (HDs) can exist as the twins of CDs. The coherent interface of t-(100)gr//(11-1)cd + [010]gr//[1-10]cd observed in MD simulation was confirmed by our high-resolution transmission electron microscopy experiment. The proposed mechanism not only clarifies the role of HD in graphite-diamond transition but also yields atomistic insight into strengthening synthetic diamond via microstructure engineering.

在高压和高温条件下的石墨-金刚石转变已成为物理科学的中心课题。但是，它的原子机制仍在争论中。利用大规模分子动力学（MD）模拟，我们报道了一种机制，石墨基质中的金刚石核沿两个优选方向传播，其中石墨[120]的速度比[001]快2.5倍。因此，立方金刚石（CD）是动力学上有利的产品，而只有少数六角形金刚石（HD）可以作为CD的孪晶存在。通过我们的高分辨率透射电子显微镜实验证实了在MD模拟中观察到的t-（100）gr //（11-1）cd + [010] gr // [1-10] cd的相干界面。