Structural Disorder in TiFeSb Half-Heusler Antimonide

The DFT modeling of the TiF1+xSb solid solution revealed that composition TiFe1.375Sb with MnCu2Al structure type is more preferable than equiatomic TiFeSb which crystallizes in MgAgAs-type. At T > 873 K the formation of the two phase region containing both half-Heusler and fullHeusler phases is predicted. The composition dependence of the lattice parameter shows deviation from linearity. The calculations explain the difficulties in solid solutions formation based on TiFeSb intermetallic.