The coefficients of thermal expansion and the Gruneisen functions of trigonal and amorphous selenium in the temperature range between 10K and 300K

For trigonal selenium the coefficients of thermal expansion, alpha /sub ///, parallel to the chains, and alpha _{perpendicular to} , perpendicular to the chains, have been calculated from dilatometric measurements in the temperature range 10K to 300K. By means of values of the specific heat c_p(T) and the adiabatic elastic constants C_ik(T) from literature the Gruneisen functions gamma _in and gamma /sub /// have been computed in the quasiharmonic approximation. For vitreous selenium the coefficient of thermal expansion has been measured in the same temperature range. The Gruneisen function has been calculated from data of specific heat and the adiabatic bulk modulus K_s evaluated from ultrasound measurements. For comparing the thermomechanical behaviour of vitreous and trigonal selenium, respectively, the temperature dependent Gruneisen functions are discussed by means of a linear chain model.