Per issue #141, contrast calculator now calculates the volumes of added solvent components using an element lookup table (below). However, when this method is used, as opposed to calculating the volume from the mass density and molecular weight, the solvent x-ray SLD values do not agree with those from the literature (Emilie Mahieu and Frank Gabel, Acta Cryst. (2018). D74, 715–726; https://doi.org/10.1107/S2059798318005016) when the concentration of the solvent component is high, i.e., >= 1M. At concentrations < 1M, the effect is small and the disagreement with the literature values wasn't noticed since high concentrations of solvent components are mostly used for x-ray contrast variation. Contrast calculator already uses mass density and molecular weight to calculate the SLD of solute molecules that are not protein, RNA or DNA. (The MULCh software allows this option for both solute and solvent components, but contrast calculator doesn't have an option to use the element lookup table for solute components.)
Add an option to contrast calculator to allow users to have the choice to either calculate the SLD values using the lookup table (present method) or to supply a mass density value so the the volume of the compound is calculated from the mass density and molecular weight. Test to determine the effect of high solvent component concentration on both x-ray and neutron SLDs. Provide a table and/or example to include in the contrast calculator documentation so users can make an informed choice about which option to use.
Per issue #141, contrast calculator now calculates the volumes of added solvent components using an element lookup table (below). However, when this method is used, as opposed to calculating the volume from the mass density and molecular weight, the solvent x-ray SLD values do not agree with those from the literature (Emilie Mahieu and Frank Gabel, Acta Cryst. (2018). D74, 715–726; https://doi.org/10.1107/S2059798318005016) when the concentration of the solvent component is high, i.e., >= 1M. At concentrations < 1M, the effect is small and the disagreement with the literature values wasn't noticed since high concentrations of solvent components are mostly used for x-ray contrast variation. Contrast calculator already uses mass density and molecular weight to calculate the SLD of solute molecules that are not protein, RNA or DNA. (The MULCh software allows this option for both solute and solvent components, but contrast calculator doesn't have an option to use the element lookup table for solute components.)
Add an option to contrast calculator to allow users to have the choice to either calculate the SLD values using the lookup table (present method) or to supply a mass density value so the the volume of the compound is calculated from the mass density and molecular weight. Test to determine the effect of high solvent component concentration on both x-ray and neutron SLDs. Provide a table and/or example to include in the contrast calculator documentation so users can make an informed choice about which option to use.