Calculation of chemical reaction energies using the AM05 density functional

We present results that compare the accuracy of the AM05 density functional (Armiento and Mattsson, Phys Rev B 2005, 72, 085108; Mattsson et al., J Chem Phys 2008, 128, 084714) to a set of chemical reaction energies. The reactions were generated from the singlet species in the well-known G2 test suite (Curtiss et al., J Chem Phys 1991; Curtiss et al., J Chem Phys 1997; 106, 1063). Our results show that, in general, the AM05 functional performs nearly as well as the other "pure" density functionals, but none of these perform as well as the hybrid B3LYP functional. These results are nonetheless encouraging because the AM05 functional arises from very simple assumptions, and does not require the calculation of the Hartree-Fock exchange integrals.