where w(x) are grid integration weights (typically generated along with the grid itself , but which could be taken as the volume of the Voronoi cell of x). The basins of attraction for the electron density of a benzene molecule are shown in Fig. . Near to the z = 0 plane (Fig. , top) the basins of attraction are delimited into six wedges, each containing a single H basin and a single C basin, according to the sixfold rotational symmetry of benzene. However, further from the nuclei some points are assigned to basins of attraction outside of their wedge (Fig. , bottom, white circle). For the coarse grids specified in Sec. II E 1, this misassignment affects approximately 1% of the points. However, as these points are in regions of low electron density, the error in Bader charges resulting from this misassignment is of the order of 1/1000 th of an electron. The convergence of Bader charges as a function of grid size is investigated in detail in Sec. II H 1.