Bonding and elastic properties of superconducting MgB2

Bonding and elastic properties of the recently discovered superconductor MgB2, have been studied from first-principles. Calculated lattice parameters, bulk modulus and its pressure derivative are in excellent agreement with the recently reported experimental data. Values of all independent elastic constants (c11, c12, c13, c33, and c55) as well as bulk moduli in the a and c directions (Ba and Bc, respectively) are predicted. Based on an analysis of the electron localization function we show that the bonding in the system is diverse and anisotropic. This explains the high anisotropy of the calculated elastic moduli, indicating that MgB2 should be rather brittle.