  Non-equilibrium Molecular Dynamics (NEMD) calculations of the bulk viscosity
of the triple point Lennard-Jones fluid are performed with the aim of
investigating the origin of the observed disagreement between Green-Kubo
estimates and previous NEMD data. We show that a careful application of the
Doll's perturbation field, the dynamical NEMD method, the instantaneous form of
the perturbation and the "subtraction technique" provides a NEMD estimate of
the bulk viscosity at zero field in full agreement with the value obtained by
the Green-Kubo formula. As previously reported for the shear viscosity, we find
that the bulk viscosity exhibits a large linear regime with the field intensity
which confirms the Lennard-Jones fluid as a genuine Newtonian fluid even at
triple point.
