Optical properties of emeraldine salt polymers from ab initio calculations: comparison with recent experimental data.

We present absorption coefficient, transverse dielectric function, optical conductivity, and reflectance calculated for an emeraldine salt conducting polymer in its crystalline three-dimensional polaronic structure. We utilize Kohn-Sham DFT electronic wavefunctions and energies implemented in the expression of the macroscopic transverse dielectric function in the framework of the band theory. Contributions of intra-band transitions are taken into account by adding a Drude-like term to the dielectric function calculated ab initio. Comparison with optical properties, recently measured on high-quality emeraldine salts [Nature, (2006), 441, 65], and with optical absorption spectra, recorded on other emeraldine salts, is very satisfactory. The calculated spectra are discussed in terms of energy-band structure, density of states, inter- and intra-band transitions and transverse dielectric function.