  The importance of calculating pressure profiles across liquid interfaces is
increasingly gaining recognition, and efficient methods for the calculation of
long-range contributions are fundamental in addressing systems with a large
number of charges. Here, we show how to compute the local pressure contribution
for mesh-based Ewald methods, retaining the typical N log N scaling as a
function of the lattice nodes N. This is a considerable improvement on existing
methods, which include approximating the electrostatic contribution using a
large cut-off and the, much slower, Ewald calculation. As an application, we
calculate the contribution to the pressure profile across the water/vapour
interface, coming from different molecular layers, both including and removing
the effect of thermal capillary waves. We compare the total pressure profile
with the one obtained using the cutoff approximation for the calculation of the
stresses, showing that the stress distribution obtained by the Harasima and
Irving-Kirkwood are quite similar and shifted with respect to each other at
most 0.05~nm.
