Simulation of polyethylene oxide: Improved structure using better models for hydrogen and flexible walls

We describe calculations of the structure of amorphous polyethylene oxide u sing a previously reported model, but with better treatment of hydrogen pos itions and in a code which allows relaxation of stresses in the polymerized sample by Rahman-Parrinello techniques. We also report the effects of two different intermolecular force field potentials and find that our earlier, empirical force field produces better agreement with experimental neutron s cattering results than a force field derived from ab initio electronic stru cture calculations. (C) 2001 American Institute of Physics.