Distinct liquid phase in metal-cluster superlattice solids

Variable temperature x-ray diffraction and differential scanning calorimetr y experiments on the superlattice solids of alkanethiol protected silver na noclusters show that the translational periodicity collapses around 398 K r esulting in a liquid phase, which upon cooling, reverts into the parent cry stalline phase. This reversibility is seen in a narrow temperature window o f 400-448 K. If the heating is done above 473 K, the reversibility is lost, and the liquid in the cooling cycle freezes into a disordered phase. The s tability of different phases, encountered in the experiments, is discussed in terms of a phenomenological free energy.