Cmcm structure or the 160 reflection in the monoclinic P 2 1 /c structure and would hence not split, the stronger reflection corresponds to the 134 reflection in the orthorhombic crystal structure and should split into the -242 and 142 reflections in the monoclinic structure, which should be roughly of equal intensity. There is, however, no sign of such splitting, indicating that the Sn 2+ /Sb 3+ disorder introduced during sample preparation is static. This suggests that once the crystal has been synthesized, the energy barrier for cation rearrangement along the metal-sulfur chains is too large to permit rearrangement to the predicted athermal ground-state structure at room temperature.