The Gordon Conference on Liquids has a long history of excellence. Its patrons are heavily theoreticians with interest in the newest phenomenological discoveries which might offer both challenge to interpretation and opportunity for development of new theoretical techniques. The Chairing alternates between theoreticians and experimentalists, and this year the job falls to an experimentalist, the author of this document.
The conference has frequently given much emphasis to high temperature liquid phenomena, and for years was greatly influenced by the widespread interest in critical systems. Recently there has been a tendency to return to lower temperature systems with some emphasis on complex behavior originating in amphiphilic constituents, including self assembly.
The conference this year will also have an emphasis on systems with phase transitions but the focus will shift towards molecularly simple systems which exhibit provocative behavior because of the temperature regime in which they are studied, or of the manner in which their particle interactions promote a new type of critical behavior, this time at low temperatures. Thus, in addition to examining typical fast processes and their resolution at lower temperatures into distinguishable diffusive and oscillatory modes we will hear about crossovers from the familiar free diffusion regimes to "glassy dynamics" regimes as studied by mode coupling theorists and by instantaneous normal mode analysts. Pursuing this theme, we will give a sesssion to examination of the relevance of the "landscape paradigm" to the interpretation of liquids, starting with its application to the simplest systems, namely hard sphere and square well fluids. We will also hear there about the recent resolution of an old problem, that of hard sphere packing, and its ramifications. Here, and in a succeeding session featuring evidence for microheterogeneity and clustering in fragile molecular liquids and viscous liquid metals, there develops a new way of looking at the fusion entropy.
A new type of critical phenomenon has recently been discovered and is intimately associated with the recently recognized phenomenon of polyamorphism in the glassy state. This was featured in a perspective in a recent issue of Science (Jan 17) and concerns the occurrence of phase transitions in certain isotropic liquids, most importantly water and silicon, in a phenomenology reminiscent of liquid crystals but replacing the orientational ordering of the latter with a density ordering due to the possibility of very different short range orders. As in the liquid crystal case the transitions are preceded by strong fluctuations in properties, this time in density and enthalpy.and in properties dependent on them We will have a session on this type of phase transition in liquids and hope to forge the link to the much researched liquid crystal phenomenology.
Phase transitions between states of different order also occur in mesoscopic amorphous systems of great interest to biophysicists and biologists. The folding transitions found in certain biopolymers, whose mechanism is currently a focus of so much attention, have much in common with the liquid-liquid phase transitions of the previous paragraph. They are usually first order in character, and in the right circumstances are completely reversible. We have a session on the phenomenology and theory of such systems, hoping that the relationship to the complexity obtained in the simple molecular systems of the earlier session may be clarified, and that the consequent importance of nucleation processes in protein folding kinetics might be brought into focus.
Then we have a session on new experimental techniques which extend our capabilities for study of liquids to new domains of high density (by diamond cell techniques for NMR and light scattering studies) and to high wave vector (by inelastic x-ray scattering).
There have recently been important developments in the understanding of the transitions which lead to the termination of liquid states, both by transition to the vapor state and transition to the crystal. We have a session highlighting these developments.
On the final day we will have a session on phase transitions in liquids driven alternatively by coulomb forces and by hydrophobism, and possibly silicophobism and will wind up with a session focused on hydrophobicity and bubbles, formation and coalescence, both in low temperature liquids and in vulcanism.
We recognize that the range of interesting phenomena in liquids is immense and that not everyone will find their special concerns addressed in the depth they would like in this program. On the other hand we hope that the subjects which are addressed will satisfy the basic requirement of being provocative in nature and expert in presentation.
