SURFACE STRESSES IN PARAFFIN AND POLYETHYLENE

Previous calculations of surface stress in polyethylene and paraffin c rystals are extended to include other experimental and computational d ata. There are significant changes in the magnitude of the stresses. F or polyethylene, these might reflect variations in the nature of the f old surface. Computational modelling yields surface stresses and energ ies that agree with the experimentally based magnitudes for paraffins but disagree with those for polyethylene. The discrepancy is not reduc ed by taking account of the effect of neighbouring crystals in the mod elling. The agreement of the paraffin modelling results with experimen t suggests that the discrepancy for polyethylene has its origins in th e model of the fold surface. This raises the possibility that modellin g can be used to investigate the nature of the fold surface.