The heat capacities of Pb2P2Se6 and Pb1.424Sn0.576P2Se6 were measured at temperatures between 10 and 320 K for the former and between 10 and 330 K for the latter. The heat capacities values were analyzed by harmonic approximation using the Debye and Einstein functions. They were calculated using 3 Debye and 7, 7, 7, 6 Einstein sets. The calculated heat capacities were in good agreement with the observed ones. (C) 2002 Elsevier Science B.V. All rights reserved.