Determining vibrational heat capacity and thermal expansivity and their change at glass-liquid transition

摘要

The vibrational parts of a liquid's heat capacity C-p and thermal expansion coefficient alpha may be determined from dynamic measurements. The C-p data for Pd40Ni40P20 and 0.4 Ca(NO3)(2)center dot 0.6 KNO3 have been analyzed accordingly, and it is found that change in the vibrational part at liquid-glass transformation is negligible. Analysis for alpha of poly(styrene) leads to the same conclusion. There is no discontinuity in the vibrational parts of C-p and alpha on structural unfreezing in the T-g range, and hence the change in C-p and alpha at T-g is almost entirely due to change in the configurational part. Crystallization decreases the vibrational part not because the molecular mobility is lost but because the density increases.