https://doi.org/10.1007/s100510050860
Director field configurations around a spherical particle in a nematic liquid crystal
Institut für Theoretische und Angewandte Physik, Universität
Stuttgart, Pfaffenwaldring 57,
70550 Stuttgart, Germany
Corresponding author: a holger@itap.physik.uni-stuttgart.de
Received:
2
November
1998
Published online: 15 July 1999
We study the director field around a spherical particle immersed in a
uniformly aligned nematic liquid crystal and assume
that the molecules prefer a homeotropic orientation at the surface of
the particle. Three
structures are possible: a dipole, a Saturn-ring, and a surface-ring
configuration, which we investigate by numerically minimizing the
Frank free energy supplemented by a magnetic-field and a surface term.
In the dipole configuration, which is the absolutely stable structure
for micron-size particles and sufficiently strong surface anchoring,
a twist transition is found and analyzed. We show that a
transition from the dipole to the Saturn ring configuration is induced
by either decreasing the particle size or by applying a magnetic field.
The effect of metastability and the occurrence of hysteresis in connection
with a magnetic field are discussed. The surface-ring configuration
appears when the surface-anchoring strength W is reduced. It is also
favored by a large saddle-splay constant K24. A comparison with
recent experiments [CITE]
gives a lower bound for W, i.e., 
for the interface of water and pentylcyanobiphenyl (5CB)
in the presence of the surfactant sodium dodecyl sulfate.
PACS: 77.84.Nh – Liquids, emulsions, and suspensions; liquid crystals / 61.30.Cz – Theory and models of liquid crystal structure / 61.30.Jf – Defects in liquid crystals
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1999
