DFT-based FEM analysis of nonlinear effects on indentation process in diamond crystal

We apply a new framework of a finite-element method (FEM) analysis with constitutive relations based on density functional theory (DFT), as an efficient method to characterize the nonlinear and anisotropic elastic deformation of single-crystal diamond. In our scheme, the stress–strain relations are obtained during FEM analysis on the fly based on the plane-wave-based DFT total-energy calculations and their numerical database is simultaneously constructed, which enables us to obtain high-precision stress without any empirical parameters even under finite strained conditions. To check its validity and accuracy, the shear deformation behavior of diamond crystal is analyzed under the strained condition. Then we examine the nonlinear effects on the indentation deformation of diamond single crystal, by comparing the results from the DFT-based constitutive relations with those from the linear elastic ones.