Pressure-dependent deformation in brittle diamond

Distinguished from ductile metals, in brittle covalent materials like diamond, hydrostatic pressure is a prerequisite for triggering the plastic deformation. Consequently, the theoretical framework rooted in equilibrium lattice proves inadequate in describing the behavior of brittle covalent materials, making it essential to include extrinsic hydrostatic pressure effects. Here, we take diamond as a model and introduce hydrostatic pressure in the calculation of generalized stacking fault energies (GSFE). A deformation mechanism transition from perfect dislocation slipping on {200} plane to the partial dislocation slipping on {111} plane when the hydrostatic pressure exceeds 100 GPa is revealed by the pressure-coupled GSFE and further authenticated by nanocompression and diamond anvil cell experiments. Such pressure-dependent deformation mechanism is attributed to the different pressure sensitivities of lattice volume expansion during different slip systems operating. Our works provide insights into the activation of slip systems in diamond at the atomic scale and a route to study the plastic deformation behavior of brittle covalent materials.