The internal energy of an equilibrium glass at 0 K

We postulate that, like that of an ordered crystal, the equilibrium structure of a glass is characterized by the magnitude of its internal energy. The excess δE°0 of this energy over that of its ordered crystal has been calculated for six glasses from their heat capacity data and a theory of defects in a glass. Its value of 1·3-6·2 kJ mol-1 represents the decrease in the heat of sublimation at 0 K when the structural order is lost. The absolute internal energy of an equilibrium glass at 0 K is equal to the sum of this δE°0 and the lattice and zero-point vibrational energies of its crystalline form. Implications of these observations for our current understanding of glass thermodynamics are pointed out.