  In this work, we report for the first time, detailed calculations of elastic
and thermodynamic properties of organic poly(3,4-ethylenedioxythiophene),
PEDOT, in an undiluted state, using PBE and PBEsol-PAW pseudopotentials within
the framework of Generalized Gradient Approximation Density Functional Theory.
Contrary to Molecular Dynamic simulations, series of PBE and PBEsol-PAW
calculations in the current work revealed the most stable state of monoclinic
structured pristine PEDOT. We determined thirteen (13) independent elastic
constants with elastic compliance which enables us to establish other elastic
properties of pristine PEDOT; the Pugh's ratio and the Vicker's hardness
calculations show small mismatches with PBE and PBEsol-PAW pseudopotentials.
The Debye temperature TD is predicted both in the PBE and PBEsol-PAW
calculations while the specific heat capacity Cv(T) follows the Dulong-Petit
curve having no mismatch with Debye model at low temperature, with PBE
predicting a higher Debye sound velocity than PBEsol-PAW. As accuracy tests
only, we performed electronic structure calculations of PEDOT and compared with
available data in the literature.
