Thermodynamic properties of solid CH(4).

The significant structures procedure of liquids has been used to calculate the thermodynamic properties of solid C(2)H(4). Two degeneracy terms were used to describe the behavior in the vicinities of the two phase transitions. The calculated entropy and specific heat agree well with experimental results from a few kelvins to the melting point. Less satisfactory agreement is obtained for compressibility and thermal expansion coefficients. This simple model represents surprisingly well the phase transitions in the solid state.