Torsional potential of π-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 π-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 π-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.