| Abstract: | A series of energy calculations have been carried out in order to describe the epitaxial crystallization of polyethylene from solution in terms of molecular interactions. The total energy has been computed as the sum of electrostatic, dispersion, and repulsion contributions. The potential energy associated with a section of a planar-zigzag polyethylene chain has been determined for various orientations and positions above three different planar alkali halide substrates. Inspection of the energy surfaces as a function of the spatial degrees of freedom reveals that the minimum energy orientation of the chain is that for which it is parallel to the substrate (001) cleavage plane] and aligned in the 〈110〉 direction on the surface, a result in accordance with available experimental evidence. Specifically, the chain preference is to position itself along rows of positive ions, whereas alignment along rows of negative charge appears energetically unfavorable. The mode of chain orientation is virtually independent of lattice matching criteria. Dispersionrepulsive forces have been found to be most sensitive to orientation and greater in magnitude than the electrostatic forces. |
