We present the first full-dimensional water model entirely derived from �first principles�. The model, HBB2-pol, is built upon the many-body expansion of the molecular interactions. Explicit 2-body and 3-body terms are accurately fitted using high-degree polynomials to CCSD(T)/aug-cc-pvtz reference data corrected for the basis set superposition error. The 2-body interaction transitions at intermediate range into a sum of electrostatic and dispersion interactions, reproducing the correct asymptotic behavior. The induction contributions to non-pairwise additive interactions are taken into account using Thole-type point polarizable dipoles on all atomic sites. HBB2-pol reproduces the vibration-rotation tunneling spectrum, and both 2nd and 3rd virial coefficients. Excellent agreement is found with the available state-of-the-art quantum mechanical calculations for water clusters with up to six molecules. Importantly, quantum dynamics simulations carried out with path-integral methodologies indicate that HBB2-pol accurately describes both structural and dynamical properties of the liquid phase. The predictive power of the HBB2-pol quantum simulations thus opens the door to the long-sought molecular-level picture of the unique properties of water under different conditions and in different environments.

Toward a universal water model: From the dimer to the liquid phase at the CCSD(T) level

245th National Meeting (2013)

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