Conformational energy short-range contributions

The local conformational preferences of a PE chain are described by more complicated torsion potential energy functions than those in a random walk. The simulation must not only establish the coordinates on the 2nnd lattice of every second carbon atom in the initial configurations of the PE chains, but must also describe the intramolecular short range interactions of these carbon atoms, as well as the contributions to the short-range interactions from that... 

The remainder of this section discusses several important classes of calculations in which the PB model has been, or will be, used to compute short-range electrostatic interactions. In understanding these examples, it is helpful to keep in mind the following unifying principle. Within the PB model, the electrostatic energy of a molecule or system of molecules in solution is the sum of two contributions the electrostatic interaction energy of the solute atoms, computed using Coulomb s law and the dielectric constant of the solute interior, and the electrostatic interaction between the atoms and the solvent. The first term is simple to compute and depends only on the conformation of the system under study. The second term is the one that is difficult to compute. It depends on both molecular conformation and the nature of the solvent. All the examples in this section may be viewed as varied applications of this principle. 

Fig. 38. Temperature dependence of the interfacial tension of the pure polymer for chain length N = 10. Circles correspond to MC results and the solid line to the SCF ealculations. The line with diamonds shows the the result of a density functional calculation, which uses the TPTl-equation of state, decomposes the interaction free energy functional into a repulsive short-ranged and an attractive long-ranged contribution, and employs a partial enumeration scheme to take due account of the chain conformations on all length scales [154]. The dashed line shows the result of density functional calculations which do not use the decomposition of the free energy functional, but employ the same equation of state and chain model [99]. The inset compares the free energy densities / = F/VkgT of the SCF calculations and the accurate TPTl equation of state. Adapted from [99,154]...

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