This model is an extension for global modeling of the Sedfit model for non-ideal sedimentation. It considers both concentration sedimentation and concentration-dependent diffusion constants. See the corresponding Sedfit website for details. It is described also in detail in
Solovyova, A., P. Schuck, L. Costenaro, C. Ebel (2001) Non-ideality by sedimentation velocity of halophilic malate dehydrogenase in complex solvents. Biophys. J. 81:1868-1880
In Sedphat it is implemented for sedimentation velocity data, only.