High and low density patches in simulated liquid water

Ansari, Narjes; Dandekar, Rahul; Caravati, S.; Sosso, Gabriele C.; Hassanali, Ali

doi:10.1063/1.5053559

Cited by 41 publications

(71 citation statements)

References 82 publications

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“…Using the Voronoi-void network we have found that liquid water is characterized by a large proportion of small spherical voids and large fractal or dendritic like voids at ambient conditions. 44 Voids have allowed us to identify the inhomogeneities in density, generated by fluctuations in a manner where anisotropies can be seen in a very chemically intuitive manner. The use of Voronoi-voids to examine the role of geometry on packing in simple liquids has previously been highlighted by Sastry and co-workers.…”

Section: Introductionmentioning

confidence: 99%

Insights into the Emerging Networks of Voids in Simulated Supercooled Water

et al. 2020

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The structural evolution of supercooled liquid water as we approach the glass transition temperature continues to be an active area of research. Here, we use molecular dynamics simulations of TIP4P/Ice to study the changes in the connected regions of empty space within the liquid which we interrogate using the Voronoi-voids network.We observe two important features: supercooling enhances the fraction of non-spherical voids and different sizes of voids tend to cluster forming a percolating network. By examining order parameters such as the local structure index (LSI), tetrahedrality and topological defects, we show that water molecules near large void clusters tend to be slightly more tetrahedral than those near small voids, with a lower population of underand over-coordinated defects. We show further that the distribution of closed rings of water molecules around small and large void clusters maintain a balance between 6 1 and 7 membered rings. Our results highlight the changes of the dual voids and water network as a structural hallmark of supercooling which provides insights into the molecular origins of cooperative effects that underlie density fluctuations occurring on the sub-nanometer and nanometer length scale. The percolation of the voids and the hydrogen bond network around the voids, may serve as useful order parameters to investigate density fluctuations in supercooled water.

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Section: Introductionmentioning

confidence: 99%

Insights into the Emerging Networks of Voids in Simulated Supercooled Water

et al. 2020

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“…Different local and global order parameters have been used in order to assess the presence of low-and highdensity regions in liquid water 26,27 . Recently, coexisting low-and high-density regions in ambient water have been identified using Voronoi voids on a larger length scale of 1-2 nm than those predicted by local order parameters and those reported previously 19 . Atomistic simulations showed that the low-and high-density regions are formed around the regions of empty space within the hydrogen-bond network, occurring as a result of thermal fluctuations 18 .…”

Section: E Zakhvataev 12* and L A Kompanietsmentioning

confidence: 71%

“…It should be noted that in many cases density variations will have sizes both smaller and larger than the indicated average size 8,16 . (iii) The length scale of low-and high-density regions in ambient water identified using Voronoi voids was found to be 1-2 nm 19 .…”

Section: Resultsmentioning

confidence: 92%

On the existence of soliton-like collective modes in liquid water at the viscoelastic crossover

Zakhvataev

Kompaniets

2021

Sci Rep

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The problem of large-density variations in supercooled and ambient water has been widely discussed in the past years. Recent studies have indicated the possibility of nanometer-sized density variations on the subpicosecond and picosecond time scales. The nature of fluctuating density heterogeneities remains a highly debated issue. In the present work, we address the problem of possible association of such density variations with the dynamics of terahertz longitudinal acoustic-like modes in liquid water. Our study is based on the fact that the subpicosecond dynamics of liquid water are essentially governed by the structural relaxation. Using a mode coupling theory approach, we found that for typical values of parameters of liquid water, the dynamic mechanism coming from the combination of the structural relaxation process and the finiteness of the amplitude of terahertz longitudinal acoustic-like mode gives rise to a soliton-like collective mode on a temperature-dependent nanometer length scale. The characteristics of this mode are consistent with the estimates of the amplitudes and temperature-dependent correlation lengths of density fluctuations in liquid water obtained in experiments and simulations. Thus, the fully dynamic mechanism could contribute to the formation and dynamics of fluctuating density heterogeneities. The soliton-like collective excitations suggested by our analysis may be relevant to different phenomena connected with supercooled water and can be expected to be associated with some ultrafast biological processes.

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“…In order to identify the above mentioned cages, we have used a methodology based on the Voronoi S-network, which is a generalization of the Voronoi-Delaunay tessellation for multicomponent systems [30][31][32][33] . This approach has been used in the past to identify regions of empty space in semiconducting alloys 34 , to study density fluctuations in supercooled liquids [35][36][37] and even to investigate proton diffusion in water 38 . The relevant methodological details can be found in Refs.…”

Section: Methodsmentioning

confidence: 99%

Modelling the interactions and diffusion of NO in amorphous SiO₂

Mistry

Cottom

Patel

et al. 2021

Modelling Simul. Mater. Sci. Eng.

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Nitric oxide (NO) is often used for the passivation of SiC/SiO 2 metal oxide semiconductor (MOS) devices. Although it is established experimentally, using XPS, EELS, and SIMS measurements, that the 4H-SiC/SiO 2 interface is extensively nitridated, the mechanisms of NO incorporation and diffusion in amorphous (a)-SiO 2 films are still poorly understood. We used Density Functional Theory (DFT) to simulate the incorporation and diffusion of NO through a-SiO 2 and correlate local steric environment in amorphous network to interstitial NO (NO i) incorporation energy and migration barriers. Shapes and volumes of structural cages in amorphous structures are characterised using a methodology based on the Voronoi Snetwork. Using an efficient sampling technique we identify the energy minima and transition states for neutral and negatively charged NO i molecules. Neutral NO i interacts with the amorphous network only weakly with the smallest incorporation energies in bigger cages. On the other hand NO −1 i binds at the network sites with wide O-Si-O bond angles, which also serve as the intrinsic precursor sites for electron trapping.

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High and low density patches in simulated liquid water

Abstract: Please refer to published version for the most recent bibliographic citation information. If a published version is known of, the repository item page linked to above, will contain details on accessing it.

Cited by 41 publications

References 82 publications

Insights into the Emerging Networks of Voids in Simulated Supercooled Water

Insights into the Emerging Networks of Voids in Simulated Supercooled Water

On the existence of soliton-like collective modes in liquid water at the viscoelastic crossover

Modelling the interactions and diffusion of NO in amorphous SiO₂

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High and low density patches in simulated liquid water

Abstract: Please refer to published version for the most recent bibliographic citation information. If a published version is known of, the repository item page linked to above, will contain details on accessing it.

Cited by 41 publications

References 82 publications

Insights into the Emerging Networks of Voids in Simulated Supercooled Water

Insights into the Emerging Networks of Voids in Simulated Supercooled Water

On the existence of soliton-like collective modes in liquid water at the viscoelastic crossover

Modelling the interactions and diffusion of NO in amorphous SiO2

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Product

Resources

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Modelling the interactions and diffusion of NO in amorphous SiO₂