Physikalische Chemie - Direktor: Prof. Dr. Martin Wolf
Department Seminar
Host: M. Sajadi

Monday, January 22, 2018, 11:00 am
All are invited to meet around 10:40 am for a chat with coffee & cookies.
PC Seminar Room, G 2.06, Faradayweg 4
Prof. Lars Pettersson
Theory, Chemical Physics Group, Department of Physics, AlbaNova University Center, Stockholm University
A Two-State Picture of Water and the Funnel of Life
I will discuss recent experimental and simulation data of liquid water and the picture of fluctuations between high-density (HDL) and low-density (LDL) liquid this has led to [1,2]. The HDL would be a more close-packed form, favored by entropy and dominates at high temperature. Below about 50°C correlated fluctuations into tetrahedral (LDL) struc-tures, favored by hydrogen-bonding (enthalpy), begin to appear and become increasingly important upon further cooling [3,4]. A coexistence line between the two liquid phases is hypothesized, but it must lie at high pressure and low temperature in the so-called “No-man’s land” where measurements are extremely challenging due to rapid crystallization [5,6]. If such a line exists, it may terminate in a critical point from which a funnel-like region of enhanced fluctuations between the two forms emanates. Indeed, in a very recent study the isothermal compressibility and correlation length were measured down to 227 K and shown to exhibit a maximum which can be viewed as a trace of a critical point[7]. Since these fluctuations are observed up to ambient conditions we may live in what could be called the “funnel of Life”. In light of this picture I will discuss some of the more important anomalous properties of water..
[1] Anders Nilsson and Lars G.M. Pettersson, The Structural Origin of Anomalous Properties of Liquid Water, Nature Commun. 6, 8998 (2015)..
[2] P. Gallo et al., Water: A Tale of Two Liquids, Chem. Rev. 116, 7463-7500 (2016).
[3] L. B. Skinner et al., The Structure of Water Around the Compressibility Minimum, J. Chem. Phys. 141, 214507 (2014).
[4] D. Schlesinger, K.T. Wikfeldt, L.B. Skinner, C.J. Benmore, A. Nilsson and L.G.M. Pettersson, The temperature dependence of intermediate range oxygen-oxygen correlations in liquid water, J. Chem. Phys. 145, 084503 (2016).
[5] J. A. Sellberg et al., Ultrafast X-ray probing of water structure below the homogeneous ice nucleation temperature, Nature 510, 381 (2014).
[6] F. Perakis et al., Diffusive dynamics during the high- to low-density transition in amorphous ices, Proc. Natl. Acad. Sci. 114, 8193 (2017).
[7] Kim, K.-H. et al. Maxima in the Thermodynamic Response and Correlation Functions of Deeply Supercooled Water, Science 358, 1589 (2017).