The aim of our research
This project is a part of the Glass and Time.
The glass transition is a universal phenomenon which in its essence is
independent of the interactions between the atoms or molecules of the
liquid forming the glass. The universal character of the transition
has led physicists to believe that there is one underlying simple
explanation of the phenomenon. More than 15 years ago the Nobel
laureate P.W. Anderson stated that understanding the glass-transition
is deepest unsolved problem in solid state physics [1], but a
satisfactory explanation is still lacking. Understanding the
glass-transition implies understanding the dynamics (eg. diffusion,
vibration, relaxation) and the physics in general of the viscous
liquid forming the glass. Gasses can to a great extend be understood
via the ideal gas model where the interactions between particles are
ignored. In crystalline solids the physics can be understood by
exploding the periodic nature of the structure. No similar
simplification can be made for liquids. Here we need to consider the
interaction between the molecules, the kinetic energy and the
amorphous structure. This is a challenge to a model systems or a
theory explaining the glass transition and the physics of liquids in
general.
The "Glass and Time" group on RUC has during the last five years
succeeded in identifying a class of simple liquids and a theory for
describing these has been developed [2]. This theory, called the
isomorph theory, has proven very effective in describing computer
simulated liquids with simple interactions (e.g. Lennard Jones
liquids). But how useful is the theory when it comes to understanding
the physics the liquids we deal with in the laboratory? In 2011 we
published the first experimental results supporting the isomorph
theory [3]. Here we showed how the relative effect of density and
temperature on the glass transition can be understood in terms of the
isomorph theory. There are several other predictions of the theory,
many of these are directly related to the glass transition. Our
current and future experimental work aims at testing these
predictions.
The tools used are mainly dielectric spectroscopy and neutron
scattering. The control of temperature as well as pressure plays an
important role in all our studies.
[1] Science 267, 1609 (1995)
[2] J. Chem. Phys. 131, 234504 (2009)
[3] Nature Physics 7, 816 (2011)
