Stable and metastable mixed crystals in the orientationally disordered (OD) state of the 2-methyl-2 chloro-propane ((CH3)(3)CCl) + 2, 2-dichloropropane ((CH3)(3)CCl2) binary system were characterized from crystallographic and thermodynamic points of view. Large concentration domains of stable rhombohedral (R) and metastable face-centered cubic (FCC) mixed crystals were found despite the non-isomorphism relationship between the stable FCC phase of (CH3)(3)CCl and the stable R phase of (CH3)(2)CCl2. In addition, a third OD phase region was observed in the (CH3)(2)CCl2-rich side of the system. It is simple cubic (SC) and metastable with respect to the stable R phase region. This corresponds to the binary extension of the R-SC stable-metastable relationship found for pure (CH3)(2)CCl2. (C) 2002 Elsevier Science B.V. All rights reserved.