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Title: Quasielastic neutron scattering measurements and ab initio MD-simulations on single ion motions in molten NaF

The ionic stochastic motions in the molten alkali halide NaF are investigated by quasielastic neutron scattering and first principles molecular dynamics simulation. Quasielastic neutron scattering was employed to extract the diffusion behavior of the sodium ions in the melt. An extensive first principles based simulation on a box of up to 512 particles has been performed to complement the experimental data. From that large box, a smaller 64-particle box has then been simulated over a runtime of 60 ps. A good agreement between calculated and neutron data on the level of spectral shape has been obtained. The obtained sodium diffusion coefficients agree very well. The simulation predicts a fluorine diffusion coefficient similar to the sodium one. Applying the Nernst-Einstein equation, a remarkable large cross correlation between both ions can be deduced. The velocity cross correlations demonstrate a positive correlation between the ions over a period of 0.1 ps. That strong correlation is evidence that the unlike ions do not move completely statistically independent and have a strong association over a short period of time.
Authors:
 [1] ;  [1] ;  [2]
  1. ISIS Facility, Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom)
  2. (United Kingdom)
Publication Date:
OSTI Identifier:
22493620
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 144; Journal Issue: 1; Other Information: (c) 2016 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; COMPUTERIZED SIMULATION; CORRELATIONS; DIFFUSION; EINSTEIN FIELD EQUATIONS; FLUORINE; MOLECULAR DYNAMICS METHOD; NEUTRON DIFFRACTION; QUASI-ELASTIC SCATTERING; SODIUM; SODIUM FLUORIDES; SODIUM IONS; STOCHASTIC PROCESSES; VELOCITY