Postgraduate Seminar Series
Thursday 29th January
Room 564
5pm
Small Angle Neutron scattering on the anisotropic
superconductor CaC6.
By Andrew Crichton
Small-angle neutron scattering has been applied to
study the vortex lattice in the intercalated graphite
superconductor CaC6 Tc=11.3 K. Scattering from
the vortex lattice is in the form of a ring, reflecting
the absence of in-plane orientational order of the
pyrolitic graphene planes. The temperature and
field dependence of the scattered intensity allows
the in-plane zero temperature value of the
coherence length and the London penetration
depth to be estimated. The orientation of the
vortex lattice is fixed relative to the rotation axis
of the crystal as predicted by anisotropic London
theory.
Monte Carlo Simulations of Polymers near surfaces
By Adam Swetnam
Very simple models are sufficient to capture the behaviour
of polymer molecules. This allows advanced Monte Carlo
techniques such as the Wang-Landau algorithm to be
applied. This algorithm determines the density of states of a
system, which allows its properties to be determined at all
temperatures. Particularly useful is the specific heat
capacity as peaks in this indicate phase transitions. For
polymers near surfaces the density of states can be
determined as a function of self interaction energy and
surface interaction energy, from this the specific heat
capacity can be determined as a function of two variables
which allows a phase diagram to be plotted. There is a
problem with this method as in order to get the density of
states to converge the polymer must be confined but we
have determined a way to overcome this problem.
The postgraduate seminar series is a series of informal talks run by
postgraduates for postgraduates. All postgraduates are welcome and
refreshments are always provided!