Heat Capacity at the Glass Transition

Abstract

The heat capacities C_p of a number of Ge_xSe_1-x amorphous alloys have been measured through the glass transition temperature T_g. In each case C_p rises from a value slightly larger than the classical limiting value of 3R in the glass to a value in the supercooled liquid which is larger by up to 40%. For x = 0.125, 0.2, 0.25 and 0.35 values of C_p in the liquid follow a common curve, identical within the experimental error to that of liquid Se. To explain this insensitivity to structure, a theory is presented for the liquid in which the contributions to the internal energy from vibrational and configurational modes are separated. By identifying the configurational modes with local stresses, an explicit expression can be calculated for the heat capacity which agrees well with experiment.