First-principles study on the upper pressure limit of diamond under multiaxial stress

In this study, we investigated the upper pressure limit of diamond. A method for predicting the upper pressure limit of diamonds under multiaxial stress is developed by introducing stress angles a based on first-principles calculations. The normal stresses of diamond in three mutually orthogonal orientations [111], [112], and [110] are set as a[111]tan(a) = a[112] = a[110]. The three most important characteristics, namely, the theoretical strength, maximum dynamic stability stress, and phase transition stress, are evaluated and analysed to further determine the upper pressure limit of diamond. The calculated results indicate that the upper pressure limit of diamond can reach up to 1.265 TPa in the [111] orientation under multiaxial compressions, which is approximately 1.25 times higher than that of our calculated phase transition stress (sigma[111] = 1008.3 GPa) and 1.18-1.28 times higher than that of the current upper pressure limit 990 (Phys. Rev. Lett. 108 (2012) 045704)-1075 GPa (Proc. Natl Acad. Sci. U. S. A. 103 (2006) 1204) at a hydrostatic pressure, which is a new record. This study provides a possible approach to obtain a high pressure limit by multiaxial compression, which will advance the progress of in-situ high-pressure anvil technology.