By the use of an iterative method the linearized phonon-Boltzmann equation for a dielectric solid subjected to a thermal gradient is solved in the frame of three-phonon interactions. In this way it is possible to calculate the thermal conductivity of rare-gas solids starting from the pair potential and accounting for the real Brillouin zone of the lattice. The numerical results are in full agreement with experiment and represent a considerable improvement with respect to those previously deduced for an isotropic solid.

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Recently we investigated the occurrence of static periodic stripes in a hybrid aligned nematic cell. Assuming that the tilt anchoring was stronger at the planar wall than at the homeotropic wall, we have found the critical thickness of the cell for the transition from planar to periodic alignment as a function of the surface energy in the presence of a magnetic field. Here we study, for the same kind of cell, the critical thickness between the periodic and the aperiodic deformed structure by means of an appropriate numerical technique. As expected, such a threshold was found to be greater than the asymptotic threshold between planar and aperiodic structures. We performed an experiment, which allowed us to give an estimate of the surfacelike elastic constant K,4.

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