Evidence of a two-state picture for supercooled water and its connections with glassy dynamics |
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Authors: | G A Appignanesi J A Rodriguez Fris and F Sciortino |
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Institution: | (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 |
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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. |
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Keywords: | PACS" target="_blank">PACS 61 20 Ja Computer simulation of liquid structure 61 20 Lc Time-dependent properties relaxation 61 25 Em Molecular liquids |
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