We introduce a parameter-free structural indicator to classify local environments of water molecules in stable and supercooled liquid states, which reveals a clear two-peak distribution of local properties. The majority of molecules are tetrahedrally coordinated (T molecules), via low-energy hydrogen bonds. The minority component, whose relative concentration decreases with a decrease in the temperature at constant pressure, is characterized by prevalently three-coordinated molecules, giving rise to a distorted local network around them (D molecules). The inter-conversion between T and D molecules explains the increasing specific heat at constant pressure on cooling. The local structure around a T molecule resembles the one found experimentally in low-density amorphous ice (a network structure mostly composed by T molecules), while the local structure around a D molecule is reminiscent of the structural properties of high-density amorphous ice (a network structure composed by a mixture of T and D molecules).

A structural indicator for water built upon potential energy considerations / Montes de Oca, Joan M.; Sciortino, Francesco; Appignanesi, Gustavo A.. - In: JOURNAL OF CHEMICAL PHYSICS ONLINE. - ISSN 1089-7690. - 152:24(2020). [10.1063/5.0010895]

A structural indicator for water built upon potential energy considerations

Francesco Sciortino;
2020

Abstract

We introduce a parameter-free structural indicator to classify local environments of water molecules in stable and supercooled liquid states, which reveals a clear two-peak distribution of local properties. The majority of molecules are tetrahedrally coordinated (T molecules), via low-energy hydrogen bonds. The minority component, whose relative concentration decreases with a decrease in the temperature at constant pressure, is characterized by prevalently three-coordinated molecules, giving rise to a distorted local network around them (D molecules). The inter-conversion between T and D molecules explains the increasing specific heat at constant pressure on cooling. The local structure around a T molecule resembles the one found experimentally in low-density amorphous ice (a network structure mostly composed by T molecules), while the local structure around a D molecule is reminiscent of the structural properties of high-density amorphous ice (a network structure composed by a mixture of T and D molecules).
2020
supercooled water, molecular dynamic simulation, glass transition
01 Pubblicazione su rivista::01a Articolo in rivista
A structural indicator for water built upon potential energy considerations / Montes de Oca, Joan M.; Sciortino, Francesco; Appignanesi, Gustavo A.. - In: JOURNAL OF CHEMICAL PHYSICS ONLINE. - ISSN 1089-7690. - 152:24(2020). [10.1063/5.0010895]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1556074
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