arXiv subjects

Robert F. Tournier

Publications and source records attributed to Robert F. Tournier.

5 recordsLinked to original sources

arXiv2019

First-order transitions in glasses and melts induced by solid superclusters nucleated and melted by homogeneous nucleation instead of surface melting

Supercooled liquids give rise, by homogeneous nucleation, to solid superclusters acting as building blocks of glass, ultrastable glass, and glacial glass phases before being crystallized. Liquid-to-liquid phase transitions begin to be observed above the melting temperature Tm as well as critical undercooling depending on critical overheating (Tm-T)/Tm. Solid nuclei exist above Tm and melt by homogeneous nucleation of liquid instead of surface melting. The Gibbs free energy change predicted by the classical nucleation equation is completed by an additional enthalpy which stabilize these solid entities during undercooling. A two-liquid model, using this renewed equation, predicts the new homogeneous nucleation temperatures inducing first-order transitions, and the enthalpy and entropy of new liquid and glass phases. These calculations are successfully applied to ethylbenzene, triphenyl phosphite, d-mannitol, n-butanol, Zr41.2Ti13.8Cu12.5Ni10Be22.5, Ti34Zr11Cu47Ni8, and Co81.5B18.5. A critical supercooling and overheating rate (Tm-T)/Tm = 0.198 of liquid elements is predicted in agreement with experiments on Sn droplets.

cond-mat.dis-nn↗

arXiv2017

Predicting Glass-to-Glass and Liquid-to-Liquid Phase Transitions in Water using Classical Nucleation Temperature

Glass-to-glass and liquid-to-liquid phase transitions are observed in bulk and confined water, with or without applied pressure. They result from the competition of two liquid phases separated by an enthalpy difference depending on temperature. The classical nucleation equation of these phases is completed by this quantity existing at all temperatures, a pressure contribution, and an enthalpy excess. This equation leads to two homogeneous nucleation temperatures in each liquid phase, the first one being the formation temperature of an ordered liquid phase below the melting temperature and the second one corresponding to the overheating temperature. Thermodynamic properties, double glass transition temperatures, sharp enthalpy and volume changes are predicted in agreement with experimental results. The first-order transition line between fragile and strong liquids joins two critical points. Glass phase above its transition temperature becomes ordered liquid phase disappearing at a first-order transition temperature at low pressure and at a temperature larger than the melting temperature at high pressure.

cond-mat.dis-nn↗

arXiv2016

Lindenmann Rule Applied to the Melting of Crystals and Ultrastable Glasses

The ratio of the mean square amplitude root of thermal vibrations and the interatomic distance is a universal constant dls at the melting temperature Tm. The classical Gibbs free energy change completed by a volume energy saving els (or Delg)*DHm that governs the liquid to solid and liquid to ultra-stable glass transformations leads to a universal constant equal to els (or Delg), DHm being the crystal melting enthalpy. The minimum values 0.217 of els and 0.103 of dls are used to predict ultra-stable glass formation in pure metallic liquid elements at a universal reduced temperature 0g = (Tg-Tm)/Tm = -0.6223.

cond-mat.mtrl-sci↗

arXiv2016

Glass phase and other multiple liquid-to-liquid transitions resulting from two liquid phase competition

Melt supercooling leads to glass formation. Liquid-to-liquid phase transitions are observed depending on thermal paths. Viscosity, density and surface tension thermal dependences measured at heating and subsequent cooling show hysteresis below a branching temperature and result from the competition of two-liquid phases separated by an enthalpy difference depending on temperature. The nucleation classical equation of these phases is completed by this enthalpy saving existing at all temperatures. The glass phase thermodynamic parameters and their thermal variation have already been determined in such a two-liquid model. They are used at high temperatures to predict liquid-to-liquid transitions in some metallic glass-forming melts.

cond-mat.mtrl-sci↗

arXiv2016

Helium-4 Glass Phase: a Model for Liquid Elements

The specific heat of liquid helium confined under pressure in nanoporous material and the formation, in these conditions, of a glass phase accompanied by latent heat are known. These properties are in good agreement with a recent model predicting, in liquid elements, the formation of ultrastable glass having universal thermodynamic properties. The third law of thermodynamics involves that the specific heat decreases at low temperatures and consequently the effective transition temperature of the glass increases up to the temperature where the frozen enthalpy becomes equal to the predicted value. The glass residual entropy is about 23.6% of the melting entropy.

cond-mat.dis-nn↗