Determination of the third-order elastic constants of diamond by shock wave simulations

A new methodology comprising finite-strain theory, Hugoniot jump conditions, second-order elastic constants (SOECs) and their pressure derivatives, has been developed and was used to estimate the third-order elastic constants (TOECs) of diamond. Density functional theory was used to compute SOECs and their pressure derivatives. The required shock wave Hugoniots were estimated along the $⟨100⟩$, $⟨110⟩$ and $⟨111⟩$ directions by classical molecular dynamics simulations. Calculated SOECs and TOECs were compared with available experimental and theoretical results. For SOECs, a fairly good agreement with experimental data was obtained and for TOECs our methodology predicts a better agreement with experimental data compared to other theoretical methods. (letter)