Phase transitions in the Cu-2-S nanowires have been studied as a function of temperature and pressure. Differential scanning calorimetry (DSC) shows an endothermic process at 101.8degreesC upon heating, corresponding to the phase transition from gamma-Cu2S (monoclinic) to beta-Cu2S (hexagonal) in the bulk (103.5degreesC). However, the reverse phase transition was found to be much lower (74.8 degreesC). X-ray diffraction (XRD) demonstrates that the c-axis of gamma-Cu2S is transformed to the c-axis of beta-Cu2S owing to the positional disorder of the Cu atoms. Two high-pressure phases of Cu,S have been identified using a diamond anvil cell and the energy-dispersive XRD technique. (C) 2002 Elsevier Science B.V. All rights reserved.