Decrease in the configurational and vibrational entropies on supercooling a liquid and their relations with the excess entropy

As a liquid is cooled, the number of configurations available to its structure decreases, the energy density of states decreases, and the anharmonic forces become less important. The first decreases the configurational entropy and the other two decrease the vibrational entropy. Interdependence of the three effects is examined. It is found that a liquid's configurational entropy would not be proportional to its excess entropy over the crystal phase. A quantitative analysis of the already resolved entropies of an N-type liquid, selenium, supports this conclusion. Therefore, the much used assumption of a liquid's configurational entropy being proportional to its excess entropy is not valid. This is in addition to the revision needed on the basis of the finding that the entropy theory's use of the Kauzmann extrapolation was based on implausible assumptions. (C) 2002 Elsevier Science B.V. All rights reserved.