Physical and Theoretical Chemistry

Biography

Biography: Robert F. Tournier

Abstract

The classical nucleation equation fails to predict the glass phases, the liquid-to-liquid phase transitions (LLPT), Lindemann’s constant, the presence of intrinsic growth nuclei above T_m inducing magnetic texturing by cooling magnetic melts in high magnetic fields, and the first-order glass transitions of liquid helium under pressure. These problems are solved adding in (1) an enthalpy saving e×DH_m associated with the formation of spherical growth nuclei (superclusters) having the same melting temperature T_m and melting enthalpy DH_m per mole whatever their radius R is:

where  is a numerical coefficient equal to e_ls or e_gs or De_lg=(e_ls-e_gs) with the indexes l for liquid, s for solid and g for glass phases, q =(T-T_m)/T_m and q₀ is q_0l or q_0g. The glass transition is viewed as a LLPT from Phase 1 above T_g to Phase 2 below T_g. e_ls×DH_m is reduced at the glass transition with e_ls replaced by e_gs and q_0m by q_og, e_ls and e_gs being the enthalpy saving maximum coefficients associated with the homogeneous nucleation of nuclei inducing crystallization. The enthalpy change at T_g giving rise to the glass phase obeys (1) with e replaced by De_lg. All thermodynamic properties are calculated when T_g, e_ls=e_ls0 at T_m and q_0l are known. Phase 3 is relaxing in Phase 2. An enthalpy excess, due to quenching the melt or to vapor deposition, can induce sharp transitions to Phase 3. Two homogeneous nucleation temperatures q =e above T_m and q =(e-2)/3 below T_m are expected  minimizing the surface energy. Values of e have been obtained in pure liquid elements, strong and fragile glass-forming melts. In pure liquid elements, the smallest value e_ls0=0.217 leads to Lindemann’s constant equal to 0.103 at T_m. De_lg, e_ls and e_gs are used to predict LLPT between Phase 1 and Phase 2 above and below T_m even in water.