Rate dependence and anisotropy of SiC response to ramp and wave-free quasi-isentropic compression

Abstract The elastic-plastic and structural phase transitions of silicon carbide (SiC) under compression loading are investigated using large-scale molecular dynamics simulations. The ramp wave compression applied to single crystal 3C–SiC uses ramp rise times from 10 to 100 ps. Wave-free quasi-isentropic compression loading is also applied with strain rates varying from 108 to 1011 s−1. Loading is performed along three crystal orientations: [001], [110], and [111]. The effects of different ramp rise time and compressive strain rates on material response are characterized, with special attention payed to anisotropy. SiC under increasing strong ramp compression displays elastic, plastic, and structural phase transition responses. Results show that the plastic deformation and phase transition are strongly strain-rate dependent. With increasing strain rate, the threshold strain and longitudinal stress for deformation twinning is anisotropically increased. The threshold longitudinal and shear stresses triggering plasticity are lowest in [001] direction, followed by [110], and highest in [111] SiC when subjected to the same strain rate. The threshold pressure for the structural phase transition from zinc blende (ZB) to rock-salt (RS) structure increases with the applied strain rate. As a result, the transition from ZB to RS structure is incomplete and inhomogeneous mixed-phase structures are observed over a wide range of applied stresses, even up to ~180 GPa, which agrees well with experimental observations.