Our department has strong traditions in the science of molten salts and oxide glasses including research on structure, physical properties and thermodynamics. In the past the activity was strongly linked to the industrial importance of molten salt electrolysis, while we currently are concerned with the understanding of viscous slow down of liquids, which is one of the key questions in condensed matter science.

Studies of liquids, particularly during compression or supercooling, have indicated phase transitions in the liquid state and encouraged the search for polymorphic phase transitions in liquids and glasses. Tetrahedral liquids such as water and silica with an open network of corner sharing tetrahedra have been strongly linked to these exotic liquid properties. In collaboration with Professor Svein Stølen, University of Oslo, we have for some years focused a part of our research activity on GeSe₂, at network-forming semiconductor-glass, that we anticipated would show anomalous behaviour in the liquid state. An international collaboration on in-situ high-pressure high-temperature X-ray diffraction of GeSe₂ (ESRF, France) have revealed a melting point maximum of monoclinic GeSe₂ and a breakdown of intermediate range order of liquid GeSe₂ during compression. The latter was manifested by a strong suppression and complete loss of the first sharp diffraction peak. The thermodynamics of liquid GeSe₂ suggest that extensive structural disordering takes place in the liquid on heating and points to a fragile melt whereas the kinetic (viscosity) characteristics of the system close to the glass transition temperature suggests a much less fragile character (see Figure). We have proposed that the above "discrepancy" between the behaviour of the melts close to Tg and at high temperatures can be explained by a fragile-to-strong transition in supercooled GeSe₂-Se. The transition is related to the onset of chemical disorder and the density minimum of liquid GeSe₂. Of particular interest during the last decade has also been silica aerogels where our research has been focussed on strengthening of the silica network by aging processes and the preparation of aerogels at ambient atmosphere. The generic knowledge achieved about aging phenomena of wet silica gels in different liquids and at different conditions is very interesting also in many different applications of silica gels, e.g. for biomedical applications.

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