Acidification of three-dimensional emeraldine polymers: Search for minimum energy paths from base to salt

We present a numerical simulation of the HCl acidification process of a three-dimensional semiconducting Emeraldine Base (EB) polymer leading to the corresponding metallic Emeraldine Salt (ES) form. We have searched minimum energy paths connecting the initial configuration, composed by two EB polymer chains per cell each one attached by two HCl molecules, with the Pc2a polaronic configuration which is the final state of the acidification process. For this aim the variational Nudged Elastic Band method has been adopted. We provide a pictorial representation of the acidification process at T=0K monitoring the EB protonation and the evolution of the polymeric chains and of the positions of the Cl- counterions on the lowest potential energy surface. To include also temperature effects we have explored the potential energy surface around the final equilibrium configuration heating the system and following its dynamics by Car-Parrinello procedure.