Voigt grid optimization: nearest-neighbor --> interpolation (from Erwan Pannier)

[pcubillos]

You may want to give a look at our recent paper (doi/10.1016/j.jqsrt.2020.107476) where we use a similar same method, but with an actual interpolation instead of closest neighbour. Dirk computed simple and optimized coefficients, which you could use : this could allow you to use a coarser grid and therefore to improve even more the computational times