  The thermal conductivity of a model for solid argon is investigated using
nonequilibrium molecular dynamics methods, as well as the traditional Boltzmann
transport equation approach with input from molecular dynamics calculations,
both with classical and quantum thermostats. A surprising result is that, at
low temperatures, only the classical molecular dynamics technique is in
agreement with the experimental data. We argue that this agreement is due to a
compensation of errors, and raise the issue of an appropriate method for
calculating thermal conductivities at low (below Debye) temperatures.
