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https://libjncir.jncasr.ac.in/xmlui/handle/10572/1545
2024-06-15T21:16:18ZDiffusivity anomaly in modified Stillinger-Weber liquids
https://libjncir.jncasr.ac.in/xmlui/handle/10572/2536
Title: Diffusivity anomaly in modified Stillinger-Weber liquids
Authors: Sengupta, Shiladitya; Vasisht, Vishwas V.; Sastry, Srikanth
Abstract: By modifying the tetrahedrality (the strength of the three body interactions) in the well-known Stillinger-Weber model for silicon, we study the diffusivity of a series of model liquids as a function of tetrahedrality and temperature at fixed pressure. Previous work has shown that at constant temperature, the diffusivity exhibits a maximum as a function of tetrahedrality, which we refer to as the diffusivity anomaly, in analogy with the well-known anomaly in water upon variation of pressure at constant temperature. We explore to what extent the structural and thermodynamic changes accompanying changes in the interaction potential can help rationalize the diffusivity anomaly, by employing the Rosenfeld relation between diffusivity and the excess entropy (over the ideal gas reference value), and the pair correlation entropy, which provides an approximation to the excess entropy in terms of the pair correlation function. We find that in the modified Stillinger-Weber liquids, the Rosenfeld relation works well above the melting temperatures but exhibits deviations below, with the deviations becoming smaller for smaller tetrahedrality. Further we find that both the excess entropy and the pair correlation entropy at constant temperature go through maxima as a function of the tetrahedrality, thus demonstrating the close relationship between structural, thermodynamic, and dynamical anomalies in the modified Stillinger-Weber liquids. (C) 2014 AIP Publishing LLC.
Description: Restricted Access2014-01-01T00:00:00ZFree volume distribution of nearly jammed hard sphere packings
https://libjncir.jncasr.ac.in/xmlui/handle/10572/2538
Title: Free volume distribution of nearly jammed hard sphere packings
Authors: Maiti, Moumita; Sastry, Srikanth
Abstract: We calculate the free volume distributions of nearly jammed packings of monodisperse and bidisperse hard sphere configurations. These distributions differ qualitatively from those of the fluid, displaying a power law tail at large free volumes, which constitutes a distinct signature of nearly jammed configurations, persisting for moderate degrees of decompression. We reproduce and explain the observed distribution by considering the pair correlation function within the first coordination shell for jammed hard sphere configurations. We analyze features of the equation of state near jamming, and discuss the significance of observed asphericities of the free volumes to the equation of state. (C) 2014 AIP Publishing LLC.
Description: Restricted Access2014-01-01T00:00:00ZRole of Structure and Entropy in Determining Differences in Dynamics for Glass Formers with Different Interaction Potentials
https://libjncir.jncasr.ac.in/xmlui/handle/10572/2540
Title: Role of Structure and Entropy in Determining Differences in Dynamics for Glass Formers with Different Interaction Potentials
Authors: Banerjee, Atreyee; Sengupta, Shiladitya; Sastry, Srikanth; Bhattacharyya, Sarika Maitra
Abstract: We present a study of two model liquids with different interaction potentials, exhibiting similar structure but significantly different dynamics at low temperatures. By evaluating the configurational entropy, we show that the differences in the dynamics of these systems can be understood in terms of their thermodynamic differences. Analyzing their structure, we demonstrate that differences in pair correlation functions between the two systems, through their contribution to the entropy, dominate the differences in their dynamics, and indeed overestimate the differences. Including the contribution of higher order structural correlations to the entropy leads to smaller estimates for the relaxation times, as well as smaller differences between the two studied systems.
Description: Restricted Access2014-01-01T00:00:00ZNesting of thermodynamic, structural, and dynamic anomalies in liquid silicon
https://libjncir.jncasr.ac.in/xmlui/handle/10572/2539
Title: Nesting of thermodynamic, structural, and dynamic anomalies in liquid silicon
Authors: Vasisht, Vishwas V.; Mathew, John; Sengupta, Shiladitya; Sastry, Srikanth
Abstract: Anomalous behaviour in density, diffusivity, and structural order is investigated for silicon modeled by the Stillinger-Weber potential by performing molecular dynamics simulations. As previously reported in the case of water [J. R. Errington and P. G. Debenedetti, Nature (London) 409, 318 (2001)] and silica [M. S. Shell, P. G. Debenedetti, and A. Z. Panagiotopoulos, Phys. Rev. E 66, 011202 (2002)], a cascading of thermodynamic, dynamic, and structural anomalous regions is also observed in liquid silicon. The region of structural anomaly includes the region of diffusivity anomaly, which in turn encompasses the region of density anomaly (which is unlike water but similar to silica). In the region of structural anomaly, a tight correlation between the translational and tetrahedrality order parameter is found, but the correlation is weaker when a local orientational order parameter (q(3)) is used as a measure of tetrahedrality. The total excess entropy and the pair correlation entropy are computed across the phase diagram and the correlation between the excess entropy and the regions of anomalies in the phase diagram of liquid silicon is examined. Scaling relations associating the excess entropy with the diffusion coefficient show considerable deviation from the quasi-universal behaviour observed in hard-sphere and Lennard-Jones liquids and some liquid metals. Excess entropy based criteria for diffusivity and structural anomalies fail to capture the observed regions of anomaly. (C) 2014 AIP Publishing LLC.
Description: Restricted Access2014-01-01T00:00:00Z