Journal of Physical Chemistry & Biophysics
Open Access
ISSN: 2161-0398
+44 1478 350008
ISSN: 2161-0398
+44 1478 350008
Robert F Tournier
Grenoble Alps University, France
Institut N�?©el, France
Scientific Tracks Abstracts: J Phys Chem Biophys
The classical nucleation equation fails to predict the glass phases, the liquid-to-liquid phase transitions (LLPT), Lindemannâ�?�?s constant, the presence of intrinsic growth nuclei above Tm 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 �?µ�?�?�?�?Hm associated with the formation of spherical growth nuclei (super clusters) having the same melting temperature Tm and melting enthalpy �?�?Hm per mole whatever their radius R is: 3 2 1 4 ( ) 4 (1 ) 3 m m G R H R H Ï�? �?�? = �?�? �?�? �?¸ â�?�?�?µ + Ï�? +�?µ Ï�? �?�? (1 where �?µ(�?¸)= �?µ0(1-�?¸2x �?¸o-2) is a numerical coefficient equal to �?µls or �?µgs or �?�?�?µ1g=(�?µ1s-�?µgs) with the indexes l for liquid, s for solid and g for glass phases, �?¸ =(T-Tm)/ Tm and �?¸0 is �?¸0l or �?¸0g. The glass transition is viewed as a LLPT from Phase 1 above Tg to Phase 2 below Tg. �?µls�?�?�?�?Hm is reduced at the glass transition with �?µls replaced by �?µgs and �?¸0m by �?¸og, �?µls and �?µgs being the enthalpy saving maximum coefficients associated with the homogeneous nucleation of nuclei inducing crystallization. The enthalpy change at Tg giving rise to the glass phase obeys (1) with �?µ replaced by �?µlg. All thermodynamic properties are calculated when Tg, �?µls=�?µls0 at Tm and �?¸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 �?¸ =�?µ above Tm and �?¸ =(�?µ-2)/3 below Tm are expected minimizing the surface energy. Values of �?µ have been obtained in pure liquid elements, strong and fragile glass-forming melts. In pure liquid elements, the smallest value �?µls0=0.217 leads to Lindemannâ�?�?s constant equal to 0.103 at Tm. �?�?�?µlg, �?µls and �?µgs are used to predict LLPT between phase 1 and phase 2 above and below Tm even in water.
Robert F Tournier was Research Director at CNRS Grenoble in 2000. His group showed the appearance of magnetic moments in clusters of transition atoms and the existence of scaling laws for diluted spin glasses. The magnetic susceptibility of isolated impurities submitted to Kondo effect was separated from that of magnetic clusters. The disappearance of Kondo effect by antiparallel coupling of nuclear and electronic spins ½, the local spin fluctuations and electronic moments induced by nuclear moments in Praseodymium Van Vleck compounds were also discovered. The coexistence between superconductivity and ferromagnetism was studied or discovered in few compounds.