Torsional potential of pi-conjugated molecules using the localized Hartree-Fock Kohn-Sham exchange potential

We have assessed the reliability of the localized Hartree-Fock (LHF) Kohn-Sham exchange potential for the description of the torsional potential of ?-conjugated molecules. The LHF method is compared with other exchange-only energy functionals, as well as experiments and ab initio reference calculations for butadiene, biphenyl and bithiophene. Results indicate that the LHF method provides a good and system-independent description of the torsional potential of ?-conjugated molecules and it is the only functional that can be improved by the addition of a correlation term. Using the Lee-Yang-Parr correlation functional very good agreement with reference data is found.