The Green-Kubo method in the framework of equilibrium molecular dynamics (EMD) simulations is an effective method that has been widely used to calculate thermal conductivities of materials. The previous studies focused on the thermal conductivity values or the average values from repetitive simulations. Little research has been done to investigate the uncertainties of the thermal conductivities from EMD simulations. In this paper, we use solid argon as the material system to study the factors influencing the uncertainties of the predicted thermal conductivities. We find that the uncertainties decrease with the total simulation time as (ttotal)−α and increase with correlation time as (tcorre)β, where 0.48 < α, β < 0.52. We also find that the uncertainties decrease with increasing temperature, but the simulation domain size has a negligible effect. We propose some guidelines for selecting appropriate simulation parameters (e.g., the correlation time and total simulation time) to achieve a desired level of uncertainty. This work is potentially useful for future studies on calculating the thermal conductivities of materials using EMD simulations.

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