I would like gdat to compute psiscatvol using the psitbx. This is now also the way that is used in the TS routine psi_scatvol.
@osauter @ffelici I would like your opinion on this matter. The discussion is now open ...
Note: I was tempted at first to use psi_scatvol directly to avoid duplicating code but so far psi_scatvol does not allow for a vertical shift of the equilibrium.