Shear Viscosities of Sodium and Nickel from
NEMD Simulations
T. Cagin, K.A. Mansour, W.A. Goddard
Abstract
Shear viscosities of liquid sodium and liquid nickel are determined using
nonequilibrium molecular dynamics (NEMD) simulations.
The interactions between sodium ions are represented using a
density-dependent potential derived using second order perturbation
theory with an empty core local pseudopotential. Using a
432 atom system and the experimental
density at each temperature we calculated the viscosity at a number of
shear rates. The NEMD results for sodium are in better agreement with
the experiment than earlier Green-Kubo calcualtions using the same
potential.
The interactions between Nickel atoms are represented by a many-body
potential using form due to Sutton and Chen, parameters of the potentials
are modified to accurately represent phonon spectra and vacancy and
surface formation energies. Using a 500 atom system
and the experimental density at each temperature we
calculated the viscosity at a number of shear rates for nickel (T_m =
1726K) at temperature up to 3000K. The predicted visosity are in good
agreement with experiment.
Shear Viscosity of Liquid Gold, Copper, and Gold-Copper Alloy
Y. Qi, T. Cagin, K. A. Mansour, Y. Kimura, W. A. Goddard
Abstract
Using NEMD method we have calculated the shear viscosities of Au, Cu and
Au-Cu alloys at elevated temperatures.
The interactions for Cu, Au and Au-Cu alloy are
represented by a many-body potential form due to Sutton and Chen,
but the parameters for the potentials are modified
to accurately represent phonon spectra and vacancy and
surface formation energies [Kimura, Cagin and Goddard].
Using 500 atom model systems and
the experimental density at each temperature we
calculated the viscosity at a number of shear rates for the model systems
at temperatures up to 3000K. The predicted viscosity are in good
agreement with experiment. Copper-Gold alloy
simulations are carried out at
three different concentrations , 25%, 50% and 75%.
recently developed many body potentials [Kimura, Cagin, Goddard]
for FCC metals we have calculated the shear viscosities of Au, Cu and
Au-Cu alloys at elevated temperatures.