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Distributions of single-molecule properties as tools for the study of dynamical heterogeneities in nanoconfined water

Suffritti, Giuseppe Baldovino and Demontis, Pierfranco and Gulín-González, Jorge and Masia, Marco (2014) Distributions of single-molecule properties as tools for the study of dynamical heterogeneities in nanoconfined water. Journal of Physics: Condensed Matter, Vol. 26 (15). eISSN 1361-648X. Article.

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DOI: 10.1088/0953-8984/26/15/155103

Abstract

The explicit trend of the distribution functions of single-molecule rotational relaxation constants and atomic mean-square displacement are used to study the dynamical heterogeneities in nanoconfined water. The trend of the single-molecule properties distributions is related to the dynamic heterogeneities, and to the dynamic crossovers found in water clusters of different shapes and sizes and confined in a variety of zeolites. This was true in all the cases that were considered, in spite of the various shapes and sizes of the clusters. It is confirmed that the high temperature dynamical crossover occurring in the temperature range 200–230 K can be interpreted at a molecular level as the formation of almost translationally rigid clusters, characterized by some rotational freedom, hydrogen bond exchange and translational jumps as cage-to-cage processes. We also suggest a mechanism for the low temperature dynamical crossover (LTDC), falling in the temperature range 150–185 K, through which the adsorbed water clusters are made of nearly rigid sub-clusters, slightly mismatched, and thus permitting a relatively free librational motion at their borders. It appears that the condition required for LTDC to occur is the presence of highly heterogeneous environments for the adsorbed molecules, with some dangling hydrogen bonds or weaker than water–water hydrogen bonds. Under these conditions some dynamics are permitted at very low temperature, although most rotational motion is frozen. Therefore, it is unlikely, though not entirely excluded, that LTDC will be found in supercooled bulk water where no heterogeneous interface is present.

Item Type:Article
ID Code:10244
Status:Published
Refereed:Yes
Uncontrolled Keywords:Distributions of molecular properties, dynamical crossovers, molecular dynamics simulation, nanoconfined water
Subjects:Area 03 - Scienze chimiche > CHIM/02 Chimica fisica
Divisions:001 Università di Sassari > 01-a Nuovi Dipartimenti dal 2012 > Chimica e Farmacia
Publisher:IOP Publishing
eISSN:1361-648X
Deposited On:31 Oct 2014 08:14

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