Structures, Energetics, and Effects of Stacking Faults in MgB2

We investigate the structure, energetics, and effects of stacking faults in MgB₂ by means of first-principles density-functional calculations. Two structurally different stacking faults were determined with displacements of R=[01/20] and [2/3, 1/30], and formation energies calculated to be 956 and 932 erg/nm², respectively. Significant expansions were found at both stacking faults. The partial density of states showed that the B atoms in these stacking faults present large reductions in the density of states around the Fermi energy. However, due to their low density, these stacking faults may not cause a significant decrease of the transition temperature of MgB₂.