A first principles study of commonly observed planar defects in Ti/TiB system

TiB exhibits a hexagonal cross-section with growth faults on (1 0 0) planes and contains B27-B-f bicrystals. The hexagonal cross-section is presently explained by surface free energy minimization principle. We show that interfacial energy calculations explain the longer (1 0 0) facet compared to (1 0 1) type facets whereas free surface energy arguments do not provide the true picture. No quantitative explanation of stacking faults and B27-B-f interfaces in TiB exists. We show that the low formation energy of stacking faults and B27-B-f interfaces explain their abundance. The low energy barrier for Bf formation is shown to be responsible for their presence in TiB.