Surface energy and relaxation in boron carbide (101̄1) from first principles

•DFT-computed surface energy agrees with experimental average fracture surface energy.•Relatively large surface relaxation is a significant component of work of separation.•Surfaces that leaves icosahedra intact are found to be energetically unfavorable.

The surface energy of the boron carbide polytype B11Cp(CBC) for planar separations along {101̄1} was determined to be 3.21 J/m2 via first-principles density-functional computations. Surface atomic relaxations are relatively large, thereby lowering the surface energy significantly. The icosahedra are not intact on the surface, i.e., severed polyhedra are the lowest energy surface configuration. Good agreement was found with an experimental average fracture surface energy.