Cross sections for elastic collisions of low-energy positrons with tetrachloroethylene (C2Cl4) molecule

Elastic cross sections for positron scattering by tetrachloroethylene are being reported in this study. The calculations were carried out employing the Schwinger multichannel method at static plus polarization approximation, for impact energies up to 6 eV. To investigate the description of polarization effects, several calculations, with different polarization schemes, have been performed. In particular, we have investigated how the low-energy cross sections are affected by (i) increasing the number of particle and scattering orbitals; (ii) including additional functions placed in chargeless extra centers; (iii) including diffuse functions. The results at very low energy support the existence of a virtual state that becomes a bound state, as the polarization scheme is improved. The latter is in agreement with previous experimental and theoretical studies. Due to the lack of cross section data for this molecule, our present results are compared with experimental and theoretical data available in the literature for ethylene.