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Puzzles of Water: Are Quantum Effects the Answer?

Speaker

Alexei Sokolov, University of Tenessee, Knoxville & Oak Rigde National Laboratory

Time

2017.07.07 09:30-11:00

Venue

601 Pao Yue-Kong Library

Abstract

Water is the most important liquid on Earth and is essential for the life as we know it. Yet, despite its simple chemical structure, understanding many properties of water remains a great challenge. Even simulations fail miserably to describe consistently structure and dynamics of water, although they are reasonably successful in description of more complex molecules and polymers. This talk presents a new look on this problem – importance of quantum effects in properties of water. Usually we neglect any nuclear quantum effects in discussion of liquids at temperatures above ~10-20K. However, quantum effects depend exponentially on molecular mass and water is the lightest molecule existing in a liquid state at ambient conditions. Thus quantum effects might play important role. Combining neutron scattering and dielectric relaxation spectroscopy measurements we show that quantum fluctuations are indeed not negligible in deeply supercooled bulk water [1-3]. We suggest that quantum tunneling might be the origin of the water’s puzzling low-temperature behavior and of the apparent fragile-to-strong dynamic crossover [1-3]. The discovered anomalously large isotope effect in Tg of water [1] is consistent with the quantum tunneling dominating structural relaxation of water at these temperatures. Next we discuss possible role of quantum effects in dynamics of water even at ambient temperature. We emphasize that neglecting quantum effects in simulations might be the main reason of their failure in the case of water, where its light weight strongly enhances the importance of quantum effects. At the end we discuss other liquids of light molecules where quantum effects might play critical role [3].

  1. C. Gainaru, et al, PNAS 111, N49, 17402 (2014).
  2. A. L. Agapov, et al., Phys. Rev. E 91, 022312 (2015).
  3. V.N. Novikov, A.P. Sokolov, Europ. Phys. J. E 40, 11546 (2017).

Bio

Alexei Sokolov received an MS in Physics in 1981 from the Novosibirsk State University (Russia), and a PhD in Physics in 1986 from the Russian Academy of Sciences. He worked several years in Germany before joining faculty at the University of Akron, USA, in 1998. In 2009 he accepted Governor’s Chair position at the University of Tennessee and Oak Ridge National Laboratory, where he leads the Soft Matter group. He is a Fellow of the American Physical Society and of the American Association for the Advancement in Science. His current research interest focuses primarily on Dynamics of Soft Materials, including topics of the glass transition, polymer dynamics and dynamics of biological macromolecules, composite materials and materials for energy applications. He authored more than 250 papers.