Hi Nicola,

Thanks for your post here! I’ve taken a look through some catalogs most likely to have that material defined (like MISC.AGF), but it doesn’t seem to be provided with our installs. You’ll need to define a new material for sodium fluoride -- you can follow the steps in this article to do so. In case it helps, you may be able to use this reference for pulling index data on this material: Refractive index of NaF (Sodium fluoride) - Li

Let us know if you have any more questions. Thanks!