Mon, Jan 26 4:00pm to 7:00pm
2033 Young Hall
Speaker Professor C. Austen Angell
Hosted by
Dept. of Chemistry and Biochemistry, UCLA

"Liquid-Liquid, and Liquid-Glass First Order Phase Changes: Fact or Fiction?"

Abstract: That it is possible to have single-component systems in which two dense disordered fluid phases can coexist, has been known since Stell theorized about hard sphere models with repulsive shoulder potentials in 1972. More recently (in 1992), second liquid phases came into focus when Poole et al. were seeking an understanding of the strange behavior of supercooled water that had been reported by the present author and coworkers. They proposed that supercooled water was characterized by a second critical point lying out of sight below the homogeneous nucleation temperature of ice Ih. The inaccessibility of this critical point and the two-liquid region that would underlie it, have provided a rich field for argument (particularly in the last few years). In 1996, Daniel Kivelson and coworkers reported strange phenomena in a fragile liquid, triphenylphosphite, TPP, that the group had been studying since the 1970s. Held at a particular temperature close to its glass transition temperature, Tg = 176K, the liquid gradually became white and opaque, and then became clear again but with different amorphous properties. This was reported as an example of polyamorphism, meaning the existence of different amorphous phases of the same composition, which had recently been described by Aasland and McMillan.  This latter work – on an esoteric liquid near the garnet composition in the liquid oxide system Y2O3-Al2O3 – appeared to have caught the liquid-liquid transition in process.

The "glacial" phase of TPP, which the Kivelson group suggested as a possible example of the theoretically anticipated "defect-ordered phase" (and also as an apparently accessible case of polyamorphism), has attracted enormous attention – and controversy – as indeed have all subsequent attempts to identify distinct liquid phases of the same composition. This lecture will be devoted to reviewing this subject area with particular emphasis on some of the late-breaking developments, one of which involves structural transitions that peak in the thermodynamically stable domain of the liquid state. These are already of high technological importance, and promise to be much more so in the future.  


Location: 2033 Young Hall

Time: 4:00 PM


Location: 3037 Young Hall

Time: 5:15 PM