Eur. Phys. J. E 29, 305-310 (2009)
DOI: 10.1140/epje/i2009-10478-6

Evidence of a two-state picture for supercooled water and its connections with glassy dynamics

G. A. Appignanesi¹, J. A. Rodriguez Fris¹ and F. Sciortino<sup>2

1</sup>  Área de Fisicoquímica, Departamento de Química and INQUISUR, Universidad Nacional del Sur, Avenida Alem 1253, 8000, Bahía Blanca, Argentina
²  Dipartimento di Fisica and INFM-CNR-SOFT, Università di Roma “La Sapienza”, Piazzale A. Moro 2, 00185, Roma, Italy

rodriguezfris@plapiqui.edu.ar

Received 4 March 2009 / Published online 16 July 2009

Abstract

The picture of liquid water as consisting of a mixture of molecules of two different structural states (structured, low-density molecules and unstructured, high-density ones) represents a belief that has been around for long time awaiting for a conclusive validation. While in the last years some indicators have indeed provided certain evidence for the existence of structurally different “species”, a more definite bimodality in the distribution function of a sound structural quantity would be desired. In this context, our present work combines the use of a structural parameter with a minimization technique to yield neat bimodal distributions in a temperature range within the supercooled liquid regime, thus clearly revealing the presence of two populations of differently structured water molecules. Furthermore, we elucidate the role of the inter-conversion between the identified two kinds of states for the dynamics of structural relaxation, thus linking structural information to dynamics, a long-standing issue in glassy physics.

PACS
61.20.Ja - Computer simulation of liquid structure.
61.20.Lc - Time-dependent properties; relaxation.
61.25.Em - Molecular liquids.

Correspondence: rodriguezfris@plapiqui.edu.ar


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2009