Abstract: Recently, a new atomistic simulation method has been introduced, the quantum Drude oscillator model (QDO), which coarse-grains the electronic structure of a complex chemical system into a set of distributed quantum oscillators [1-5]. The model thereby contains, within Gaussian Statistics, all long range force diagrams – many-body polarization and dispersion beyond the dipole approximation as well as cross interactions – leading to high transferability across many different chemical environments. The responsiveness of the model means it can be parameterized to single molecule and dimer properties only, permitting the properties of condensed phase systems to naturally emerge as prediction. An efficient linear scale path integral method allows the method to be applied to simulate large scale condensed systems such as water [4-5] with low overhead in comparison to standard atomistic models while including all long force diagrams. In this lecture, the QDO model is described and its predictions of water’s properties from gas-liquid coexistence to the super critical regime including an outstanding prediction of critical point and temperature of maximum density, presented [5,6]. Given the model’s success, the physics underlying the model is then compared in more detail to other descriptions including dipole polarizable models, fixed point charge models, and the classical Drude model, and the reasons for the outstanding predictions of the QDO treatment discussed in a form a suitable for the general audience. 1. “Low variance energy estimators for systems of quantum Drude oscillators: Treating harmonic path integrals with large separations of time scales,” J. Chem. Phys. 126, 074104 (2007). 2. “Norm-conserving diffusion Monte Carlo method and diagrammatic expansion of interacting Drude oscillators: Application to solid xenon,” Phys. Rev. B, 79, 144119 (2009). 3. “Quantum Drude oscillator model of atoms and molecules: Many-body polarization and dispersion interactions for atomistic simulation,” , Phys. Rev. B 87 144103 (2013). 4. “Electronically coarse-grained model for water,” Phys. Rev. Lett. 110 227801 (2013). 5. “Signature properties of water: Their molecular electronic origins”, PNAS 112 6341 (2015). 6. “Molecular-Scale Remnants of the Liquid-Gas Transition in Supercritical Polar Fluids”, Phys. Rev. Lett. 115, 117801 (2015).

Coarse grained description of electronic structure yields water's unique properties from ice to the supercritical phase

251st National Meeting (2016)

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