Computer clock speeds are no longer increasing and increases in computational power are now limited to increases in processor number, unfamiliar territory for computational scientists who have ridden the wave of CMOS-scaling for the past 30 years. In this brave new world, gains in computational accuracy and performance will be driven by methodological development. In this lecture, a non-perturbative treatment of long range forces will be described to allow fast, transferable atomistic simulations is described with emphasis on the study of water and its phases. There are many physical systems where the non-pairwise additive nature of polarization and dispersion interactions becomes important, in particular, the complex heterogeneous systems of interest in chemistry, biology and biophysics. For example, the dipole moment of water changes from 1.85 Debye in the gas phase to approximately 2.6 Debye in the bulk liquid and attains intermediate values at hydrophobic interfaces due to many-body polarization. Similarly, although the bulk properties of hydrophobic fluids can be modeled using a pair potential, this underestimates the surface tension by 30% due to many-body dispersion interactions. In order to treat both many-body polarization and dispersion interactions in atomic and molecule systems consistently, a coarse grained electronic structure system of quantized Drude oscillators is introduced. Although they obey Gaussian statistics, the system of oscillators generates a surprisingly accurate set of electronic responses as is often the case for models based on Gaussian fluctuations in physics. A simulation method based on quantum path integrals with order O(N) computational complexity is presented to realize the model. We show how the model can treat phase diagram of water and its signature properties.Figure 1: Phase diagram of the Gaussian Coarse-grained water model (left) and its structure at T=300K

Coarse-grained Gaussian electronic structure model for water

248th National Meeting (2014)

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