Evidence of a two-state picture for supercooled water and its connections with glassy dynamicsG. A. Appignanesi1, J. A. Rodriguez Fris1 and F. Sciortino2
1 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
Received 4 March 2009 / Published online 16 July 2009
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: email@example.com
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2009