Ab initio study on the anisotropy of mechanical behavior and deformation mechanism for boron carbide

The mechanical properties and deformation mechanisms of boron carbide under a-axis and c-axis uniaxial compression are investigated by ab initio calculations based on the density functional theory. Strong anisotropy is observed. Under a-axis and c-axis compression, the maximum stresses are 89.0 GPa and 172.2 GPa respectively. Under a-axis compression, the destruction of icosahedra results in the unrecoverable deformation, while under c-axis compression, the main deformation mechanism is the formation of new bonds between the boron atoms in the three-atom chains and the equatorial boron atoms in the neighboring icosahedra.