A dispersion-corrected density functional theory case study on ethyl acetate conformers, dimer, and molecular crystal

We present a dispersion-corrected density functional theory case study on recently reported apparently difficult systems (Boese et al. in Chem Phys Chem 14: 799, 2013). The relative stability of the trans, gauche, and cis conformers of ethyl acetate, the dissociation energy of the (trans-trans) dimer, and the structure and electronic lattice energy of the corresponding molecular crystal are calculated. We utilize the generalized gradient approximation density functionals PBE and BLYP, the hybrid functional B3LYP, and the double-hybrid functional B2PLYP. It is shown that all semilocal density functionals must be corrected for missing long-range electron correlation, a.k.a. London dispersion interaction. The performance of the ab initio dispersion correction DFT-D3 is excellent and significantly improves the results compared to the uncorrected functionals and compared to the older more empirical DFT-D2 correction. The three-body dispersion contribution to the lattice energy is 7 %, while its impact on the crystal geometry and the conformer energies is negligible. A nonlocal correction approach termed DFT-NL is also tested and shows good performance comparable to the DFT-D3 results. Overall, it is shown that dispersion-corrected density functional theory can accurately describe the properties of ethyl acetate in various states ranging from single-molecule conformers to the infinite periodic molecular crystal.