The properties of fully flexible Lennard-Jones chains in the solid phase: Wertheim theory and simulation

NpT ensemble Monte Carlo simulations were performed for fully flexible Lennard-Jones chains in the solid phase. The bond length between monomers within the chains is fixed to $L=\sigma$ and the molecule is free to adopt any configuration. The solid structure of fully flexible chains is obtained by randomly locating the bonds of the chain within a face centered cubic close packed arrangement of atoms. For fully flexible chains it is believed that the stable solid phase is disordered. Such a solid is considered in this work. Computer simulations were performed for chains with $m=3, 4$ and 5 monomer units, and results were obtained for the equation of state and internal energy of the chains. An extension of Wertheim's TPT1 to the solid phase of Lennard-Jones chains (C.Vega, F.J.Blas and A.Galindo, J.Chem.Phys.,{\bf 116},7645,2002) has been proposed recently. The simulation results of this work provide a check on the performance of this theory. It is found that Wertheim's TPT1 successfully predicts the equation of state and internal energies of fully flexible LJ chains in the solid phase. Finally, a rigid LJ chain in a linear configuration has been considered. Computer simulations were also performed for the rigid chain in an ordered solid structure. It is found that fully flexible and linear rigid chains present quite different equations of state and different thermodynamic properties in the solid phase.