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Title: Thermodynamic precursors, liquid-liquid transitions, dynamic and topological anomalies in densified liquid germania

The thermodynamic, dynamic, structural, and rigidity properties of densified liquid germania (GeO{sub 2}) have been investigated using classical molecular dynamics simulation. We construct from a thermodynamic framework an analytical equation of state for the liquid allowing the possible detection of thermodynamic precursors (extrema of the derivatives of the free energy), which usually indicate the possibility of a liquid-liquid transition. It is found that for the present germania system, such precursors and the possible underlying liquid-liquid transition are hidden by the slowing down of the dynamics with decreasing temperature. In this respect, germania behaves quite differently when compared to parent tetrahedral systems such as silica or water. We then detect a diffusivity anomaly (a maximum of diffusion with changing density/volume) that is strongly correlated with changes in coordinated species, and the softening of bond-bending (BB) topological constraints that decrease the liquid rigidity and enhance transport. The diffusivity anomaly is finally substantiated from a Rosenfeld-type scaling law linked to the pair correlation entropy, and to structural relaxation.
Authors:
;  [1]
  1. Laboratoire de Physique Théorique de la Matière Condensée, Paris Sorbonne Universités, UPMC, 4 Place Jussieu, F-75252 Paris Cedex 05 (France)
Publication Date:
OSTI Identifier:
22493509
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 6; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; CORRELATIONS; DENSITY; DIFFUSION; ENTROPY; EQUATIONS OF STATE; FREE ENERGY; GERMANATES; GERMANIUM OXIDES; LIMITING VALUES; LIQUIDS; MOLECULAR DYNAMICS METHOD; PRECURSOR; RELAXATION; SCALING LAWS; SLOWING-DOWN; TEMPERATURE DEPENDENCE; TOPOLOGY; WATER