Can the Hybrid Meta GGA and DFT-D Methods Describe the Stacking Interactions in Conjugated Polymers?

Newly developed hybrid meta density functionals and density functionals augmented by a classical London dispersion term have been systematically applied for the description of stacking energy and intermolecular distance of thiophene dimer and substituted thiophene dimer. The performance of the various approaches is compared with the benchmark ab-initio calculations done with CCSD(T) (Tsuzuki el al., JACS 2002, 124, 12200). Our results indicate that, contrary to the previous DFT methods which are not reliable, the new generation of DFT performs better the stacking interactions. These functionals, and especially those with an empirical correction, are suitable for general application in conducting polymers and, in particular, the modeling of solid state in which the overlap or Pi-Pi interactions between the conjugated chains is important. (C) 2008 Wiley Periodicals, Inc. J Comput Chem 30: 1179-1184, 2009