7. If modeling dynamics or large structural changes of a solute in a solvent in the NVT ensemble, any significant changes to the size of the solute will be reflected in an overall change of the average solvent-solvent distances, creating a 'density'-contribution in the solvent-solvent scattering signal, as shown in fig. . Further treatment of this term is highly dependent on the specifics of the desired analysis. For ultra-fast studies of, say, an expanding solute, the surrounding solvent molecules might not have had time to re-arrange themselves to re-obtain the density it had before the expansion of the solute, and the term might also be present in experimental data. One can imagine other cases where the solvent has had enough time to re-equilibrate, and thus including the density term can be avoided by calculating I EV (q) from eq. 22 instead. The density term can also be eliminated by expanding the simulation cell with the increase in excluded volume, or by re-equilibrating the cell size in an NPT simulation, stopping at the same density for the previous simulation of the non-expanded solute.