For some solids, there are certain gratings predefined.
We can setup the key values to \texttt{\Lkeyword{mode}=0, 1, 2, 3 or 4} which allows to have some some gratings from very coarse \texttt{\Lkeyword{mode}=0} up to very fine \texttt{\Lkeyword{mode}=4}.
This permits us to have a draft version of a solid with \texttt{\Lkeyword{mode}=0} (fewer calculations) and then refine it with \texttt{\Lkeyword{mode}=4} for the final version.