Poisson's ratio of simple planar 'isotropic' solids in two dimensions

The influence of molecular geometry on the Poisson's ratio has been investigated for a few two-dimensional (2D) hard body systems (hard discs, hard dimers, hard cyclic trimers, and hard cyclic hexamers) forming elastically isotropic solid phases. The Poisson's ratio of the studied periodic and aperiodic solids was determined by Monte Carlo simulations using the analysis of the box fluctuations in the constant pressure ensemble (NpT) with variable box shape. The results obtained for all the studied systems showed that the Poisson's ratio grows when the density is decreased. It has been also found that the Poisson's ratio decreases with increasing number of discs in the molecule and its value for hard trimers is negative near close packing. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.