Département de chimie moléculaire

We present a comparative study of computational protocols for the description of liq. methanol from ab initio mol. dynamics simulations, in view of further applications directed at the modeling of chem. reactivity of org. and organometallic mols. in (explicit) methanol soln. We tested d. functional theory mol. dynamics (DFT-MD) in its Car-Parrinello Mol. Dynamics (CPMD) and Quickstep/Born-Oppenheimer MD (CP2K) implementations, employing six popular d. functionals with and without corrections for dispersion interactions (namely BLYP, BLYP-D2, BLYP-D3, BP86, BP86-D2, and B97-D2). Selected functionals were also tested within the two QM/MM frameworks implemented in CPMD and CP2K, considering one DFT mol. in a MM environment (described by the OPLS model of methanol). The accuracy of each of these methods at describing the bulk liq. phase under ambient conditions was evaluated by analyzing their ability to reproduce (i) the av. structure of the liq., (ii) the mean squared displacement of methanol mols., (iii) the av. mol. dipole moments, and (iv) the gas-to-liq. red-shift obsd. in their IR spectra. We show that it is difficult to find a DFT functional that describes these four properties equally well within full DFT-MD simulations, despite a good overall performance of B97-D2. On the other hand, DFT/MM-MD provides a satisfactory description of the solvent-solute polarization effects with all functionals and thus represents a good alternative for the modeling of methanol solns. in the context of chem. reactivity in an explicit environment. [on SciFinder(R)]