Network topology of deeply supercooled water. (17th November 2019)

• Record Type: Journal Article
• Authors: Shi, C.; Alderman, O. L. G.; Benmore, C. J.
• Is Part Of: Molecular physics. Volume 117:Number 22(2019)
• Page Start: 3217
• Page End: 3226
• Publication Date: 2019-11-17
• Subjects: Water -- supercooled -- liquid -- modelling -- pair distribution function; Molecules -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Molécules -- Périodiques; Chimie physique et théorique -- Périodiques; 539.6.05
• DOI: 10.1080/00268976.2019.1649492
• Languages: English
• ISSNs: 0026-8976

Abstract

Abstract : Empirical potential structure refinements have been made to recent high-energy x-ray diffraction data, providing molecular models of deeply supercooled water. The average O-O coordination number is found to drop from 5.13 at 293 K to 4.85 at 244 K, within 3.5 Å. Triplet O-O-O bond angle distributions reveal a broad peak centred at 96.4° at 293 K which shifts to 100.0° at 244 K, indicative of the local geometry becoming increasingly tetrahedral with decreasing temperature. However, although the number of non-bonded interstitial molecules between the first and second shells is depleted upon cooling, the number of interstitial molecules forming triplets that are embedded within the hydrogen bonded tetrahedral network at θ OOO = 53°, remains constant. This is consistent with previous observations of an invariant O-O coordination number with temperature (4.24 out to 3.3 Å) and corresponds to non-bonded molecules positioned at close to half the ideal tetrahedral angle. Both -O-O-O- and hydrogen-bonded -O-H-O- ring length distributions show increases in 6 and 7-membered rings upon supercooling. This is concomitant with a shift and increase in intensity of peaks at r4 ∼8.7 Å and r5 ∼10.8 Å in the oxygen-oxygen pair distribution function, which in the models correspond to correlations between adjacent and next-nearest-neighbour hydrogen-bonded rings. GRAPHICAL ABSTRACT: