Figure 2.

Box plots showing the changes in (a) density and (b) lattice parameters (a, b and c) during lattice-energy minimization of the validation set of crystal structures with the force fields. Horizontal lines of the box show the first, second (median) and third quartiles. Filled squares show the mean and whiskers indicate one standard deviation above and below the mean. Crosses indicate the maximum deviations. Structures that failed to find a minimum with the original W99 are excluded from the W99 statistics only.