Anharmonicity of the bonded O[sbnd]H group vibrations in water dimer. DFT study including dispersion interaction

Abstract

Effects of the dispersion interactions on the parameters of the water dimer equilibrium configuration and IR spectra are analyzed in the paper. Dimer equilibrium geometry was calculated using a series of the density functionals, both with (B3LYP-D3, B2PLYPD, B2PLYP-D3, mPW2PLYPD, wB97XD) and without (B3LYP, B2PLYP, mPW2PLYP, wB97X) accounting of the dispersion interactions and using density functional M-06-2X that include the dispersion interaction effects. For the determined equilibrium configurations of the water dimer, IR spectra in harmonic and anharmonic (VPT2) approximations were calculated at the corresponding levels of theory. Additional analysis of the donor hydroxyl group vibrations was performed using the 3D potential energy surfaces, calculated at B3LYP/cc-pVTZ, B3LYP-D3/cc-pVTZ, B2PLYP/cc-pVTZ, B2PLYPD/cc-pVTZ, M06-2X/cc-pVTZ, wB97XD/cc-pVTZ levels of theory. Moreover, double anharmonic couplings of the analyzed modes with other vibrational modes were accounted using the “hybrid” method. Comparison of the calculated results with the experimental and theoretical data from the literature was performed.