tau-MnAlC dilute interstitial, 4x4x2 supercell (~1.5 at% C)

Dilute-C tau-MnAlC probe: 4x4x2 L1_0 supercell with one C at the octahedral interstitial (1/2,1/2,0 of the parent cell), 2 Al at 1.792 A + 4 Mn at 1.974 A. 65 atoms, 1.5 at% C (~ realistic stabilizing dopant level, vs 33 at% in the full-C variant).