title: Prigogine-Defay ratio for an ionic glass-former: molecular dynamics simulations.
abstract: The pressure dependence of the glass-transition temperature, Tg(P), of the ionic glass-former 2Ca(NO3)2 x 3KNO3, CKN, has been obtained by molecular dynamics (MD) simulations The liquid-glass difference of thermal expansivity, deltaalpha, heat capacity, deltaCp, and isothermal compressibility, deltak, have been calculated as a function of pressure. It has been found that the Ehrenfest relation dTg/dP = TVdeltaalpha/deltaCp predicts the pressure dependence of Tg, but the other Ehrenfest relation, dTg/dP = deltakappa/deltaalpha, does not. Consequently, the Prigogine-Defay ratio, pi = deltaCpdeltakappa/TVdeltaalpha2, is n pi approximately 1.2 at low pressures, but increases 1 order of magnitude at high pressures. The pressure dependence of the Prigogine-Defay ratio is interpreted in light of recent explanations for the finding pi > 1.
authors.affiliation: Laboratório de Espectroscopia Molecular, Instituto de Química, Universidade de São Paulo, C.P. 26077, 05513-970 São Paulo, SP, Brazil.
authors.forename: Mauro C C
authors.initials: MC
authors.lastname: Ribeiro
authors.forename: Tullio
authors.initials: T
authors.lastname: Scopigno
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Ruocco