Phase Transition Mechanism of Cubic Diamond under Shock Condition

Understanding the orientation-dependent and velocity-sensitive phase transformation under shock remains a challenge. Here we study the shock responses of cubic diamond along the [001] and [111] crystal orientations using the piston shock method. Under shock compression along the [111] direction, the reduced interlayer spacing and restricted slip lead to a strength-induced phase transformation, resulting in a high-pressure intermediate structure. In contrast, shock along the [001] direction fails to induce a phase transition but leads to extensive shear deformation and the formation of twin structure. Three-dimensional contour mapping combined with microstructural evolution elucidates the formation pathway of the high-pressure intermediate phase. This anisotropic response highlights the direction-dependent mechanisms governing the structural evolution of cubic diamond under dynamic loading, offering insights for postdiamond materials design under extreme conditions.