Diffusional anomaly and network dynamics in liquid silica

Sharma, Rashmi; Mudi, Anirban; Chakravarty, Charusita

doi:10.1063/1.2219113

Cited by 38 publications

(16 citation statements)

References 37 publications

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“…For each temperature there is a ρ Dmin and a ρ Dmax and consequently a P Dmin (T) and a P Dmax (T).T h e line of P Dmax (T) in the P-T phase diagram illustrated in Fig. 5 is similar to the diffusivity maxima observed in experiments for water as well as in simulations of water (Errington & Debenedetti, 2001;Mittal et al, 2006;Netz et al, 2001), silica, (Poole et al, 1997;Sharma, Mudi & Chakravarty, 2006;Shell et al, 2002), other isotropic potentials (Xu et al, 2006;Yan et al, 2006; and for the potential Fig. 1 in the case in which the particles are monomeric (de Oliveira et al, 2006b).…”

Section: Resultssupporting

confidence: 64%

Phase Diagram and Waterlike Anomalies in Core-Softened Shoulder-Dumbbell Complex Fluids

Netz¹,

Gonzatti²,

Barbosa³

et al. 2011

Thermodynamics - Physical Chemistry of Aqueous Systems

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Section: Resultssupporting

confidence: 64%

Phase Diagram and Waterlike Anomalies in Core-Softened Shoulder-Dumbbell Complex Fluids

Netz¹,

Gonzatti²,

Barbosa³

et al. 2011

Thermodynamics - Physical Chemistry of Aqueous Systems

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“…Constructing a locus of the turning points (usually in the P T or ρT planes) generates a temperature of maximum density (TMD) line. Further anomalies are observed in, for example, the heat capacity, isothermal compressibilities and diffusivities [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] . The origins and relationships between these anomalies appear complex, potentially arising from a subtle disruption of the tetrahedral network and have been studied using accurate models for SiO 2 18,19,27,30 , BeF 2 28-30 , GeO 2 30 and H 2 O 3,6,13,[15][16][17]30,32 and their evolution traced using the Stillinger-Weber potential 33,34 and using ramp 27,[35][36][37] or core-softened 38 potentials.…”

mentioning

confidence: 99%

Liquid state anomalies and the relationship to the crystalline phase diagram

Fijan

Wilson

2019

Phys. Rev. E

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A relationship between the observation of a density anomaly and the underlying crystalline phase diagram is demonstrated. The crystal phase diagram and temperature of maximum density (TMD) lines are calculated over a range of parameter space using a Stillinger-Weber potential. Relationships between the loci of density maxima in the P T plane for the liquid state and the underlying crystalline phase diagram are investigated. Two key potential parameters are systematically varied in order to control the balance between the model two-and three-body interaction terms, and the relative effects of varying the potential parameters analysed. The respective TMD lines diverge at extreme values with one set of lines showing a re-entrant behaviour. For each parameter set the TMD lines are extrapolated to T = 0K. The corresponding pressures are related to the crystalline phase diagram and are found to lie on or near specific crystal/crystal coexistence lines for a wide range of potential parameters. The density anomaly is observed to vanish corresponding to regions in the crystal phase diagram which lack crystal/crystal coexistence lines potentially offering a new interpretation for the emergence of anomalous behaviour.

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“…Molecular dynamics (MD) simulations in the canonical (NVT) ensemble have been performed for the liquid phase of the BKS model of silica [5,14] for which computational details are given in ref. [15]. NVT-MD simulations for the Lennard-Jones (LJ) and NVT Monte Carlo simulations for the 2SRP liquid were performed using a 256-particle cubic simulation cell.…”

Section: Introductionmentioning

confidence: 99%

Entropy, diffusivity, and structural order in liquids with waterlike anomalies

Sharma

Chakraborty

Chakravarty

2006

The Journal of Chemical Physics

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185

204

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The excess entropy, S e , defined as the difference between the entropies of the liquid and the ideal gas under identical density and temperature conditions, is shown to be the critical quantity connecting the structural, diffusional and density anomalies in water-like liquids. Based on simulations of silica and the two-scale ramp liquids, water-like density and diffusional anomalies can be seen as consequences of a characteristic non-monotonic density dependence of S e . The relationship between excess entropy, the order metrics and the structural anomaly can be understood using a pair correlation approximation to S e . 61.20.Qg,05.20.Jj The behaviour of water is anomalous when compared to simple liquids for which the structure and dynamics is dominated by strong, essentially isotropic, short-range repulsions [1,2].For example, over certain ranges of temperature and pressure,the density of water increases with temperature under isobaric conditions (density anomaly) while the self-diffusivity increases with density under isothermal conditions (diffusional anomaly). Experiments as well as simulations suggest that the anomalous thermodynamic and kinetic properties of water are due to the fluctuating, three-dimensional, locally tetrahedral hydrogen-bonded network. Water-like anomalies are seen in other tetrahedral network-forming liquids, such as silica, as well as in model liquids with isotropic core-softened or two-scale pair potentials [3,4,5,6,7,8,9,10,11].In the case of liquids such as water and silica, a quantitative connection between the structure of the tetrahedral network and the macroscopic density or temperature variables can be made by introducing order metrics to gauge the type as well as the extent of structural order [6,7]. The local tetrahedral order parameter, q tet , associated with an atom i (e.g. Si atom in SiO 2 ) is defined aswhere ψ jk is the angle between the bond vectors r ij and r ik where j and k label the four nearest neighbour atoms of the same type [6]. The translational order parameter, τ , measures the extent of pair correlations present in the system and is defined aswhere ξ = rρ 1/3 , r is the pair separation and ξ c is a suitably chosen cut-off distance [12].Since τ increases as the random close-packing limit is approached, it can be regarded as measuring the degree of density ordering. At a given temperature, q tet will show a maximum and τ will show a minimum as a function of density; the loci of these extrema in the order define a structurally anomalous region in the density-temperature (ρT ) plane. Within this structurally anomalous region, the tetrahedral and translational order parameters are found to be strongly correlated. The region of the density anomaly, where (∂ρ/∂T ) P > 0, is bounded by the structurally anomalous region. The diffusionally anomalous region ((∂D/∂ρ) T > 0) closely follows the boundaries of the structurally anomalous region, specially at low temperatures. In water, the structurally anomalous region encloses the region of anomalous diffusivit...

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Diffusional anomaly and network dynamics in liquid silica

Cited by 38 publications

References 37 publications

Phase Diagram and Waterlike Anomalies in Core-Softened Shoulder-Dumbbell Complex Fluids

Phase Diagram and Waterlike Anomalies in Core-Softened Shoulder-Dumbbell Complex Fluids

Liquid state anomalies and the relationship to the crystalline phase diagram

Entropy, diffusivity, and structural order in liquids with waterlike anomalies

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