Lr. Evangelista et al., ELASTIC-CONSTANTS IN A PSEUDOMOLECULAR APPROACH FOR A MIXED MAIER-SAUPE AND NEHRING-SAUPE INTERACTION LAW, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 58(3), 1998, pp. 3245-3250
A pseudomolecular approach is employed to calculate the elastic consta
nts of a nematic liquid crystal by assuming an interaction volume of e
llipsoidal shape. We consider a special kind of mixed Maier-Saupe and
Nehring-Saupe interaction law characterized by a mixing factor epsilon
. To epsilon=0 corresponds the Maier-Saupe law, whereas to the case ep
silon=1 corresponds the induced dipole-induced dipole interaction law.
The dependence of the elastic constants on the eccentricity of the mo
lecular volume shape and on the mixing factor is investigated by means
of a numerical analysis. We show that, for particular values of the e
ccentricity, the K-11 (splay) and K-33 (bend) elastic constants become
negative for some values of the mixing factor. Moreover, the nonmonot
onic behavior of the splay-bend elastic constant with respect to the m
ixing factor, already reported in a spherical approximation for the in
teraction volume, is also observed. This result reinforces the indicat
ion that the subsurface deformations, if any, are not only due to the
splay-bend term.