Thermal conductivity of molten salt by MD simulation. Optimization of calculation conditions

We have investigated the calculation conditions necessary for precise and e fficient evaluation of the thermal conductivity of a molten salt based upon the equilibrium Green-Kubo formula by molecular dynamics simulation. The s uitable parameters are also presented for the Ewald sums in the calculation s of the interionic force and the energy current. The statistical error was estimated at +/-10 % under the calculation conditions. The dependence of t he calculated results was examined on various calculation conditions. The n umber of time steps of at least 50000, which corresponds to 200 ps, was req uired in order to obtain a fully converged value of the time integral of th e correlation functions. No significant dependence was found on the number of particles used in the simulated system compared with the statistical err or. The dependence on the time step, the interval between time origins when the correlation functions were sampled, and the upper integral limit for t he correlation functions was negligible compared with the statistical error . The addition of a small velocity vector to the ions, however, significant ly influenced the calculated value of the thermal conductivity.