Revisiting the third-order elastic constants of diamond: The higher-order effect

In this letter, we investigated the higher-order effect on the third-order elastic constants (TOECs) of diamond using longitudinal stress-uniaxial strain (LSUS) approach based on density functional theory. The result shows that the higher-order effect on TOECs is not negligible in the shock wave experiments and similar calculations, and the errors are about 28% (C111), 43% (C112), 121% (C123), 486% (C144), 56% (C155) and 75% (C456). By taking the higher-order elastic response (up to fifth order) into consideration, the convergence of TOECs against maximum strain gets improved significantly and we resolve the discrepancy of several different theoretical methods and experiments.

Automated summary

In this study, the higher-order effects on the third-order elastic constants (TOECs) of diamond were investigated using longitudinal stress-uniaxial strain (LSUS) approach based on density functional theory. The results showed that these higher-order effects are significant and cannot be neglected in shock wave experiments and similar calculations, leading to substantial errors. By considering higher-order elastic response up to fifth order, the convergence of TOECs against maximum strain was significantly improved, resolving discrepancies between various theoretical methods and experiments.