the CO molecule the value shown is the absolute value of the difference between the calculated population and the calculated population using the most dense grid. In case of the C atom in the diamond system (green line) the charge should be zero, so the absolute value of the calculated charge is presented. (b) The total number of grid points as function of the number of Lebedev-Laikov grid points per spherical shell.[@LebedevVI_grid:1999DokladyMath] The large number of grid points for the diamond system, is due to its large SoI (see text).[]{data-label="fig:HirI_nlebConv"}](nleb_conv3.png "fig:"){width="8cm"}\

Spherical integration grids S$_{sys}$ and S$_{atom}$ {#ssc:sphereIntgrid}
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Because the populations and charges in the Hirshfeld(-I) approach are obtained by an integration of the CDD of the system, attention needs to be paid to the integration grid used. The current implementation uses a multi-centered grid, as was noted in Sec. \[ssc:spatInteg\]. In this setup we used Lebedev-Laikov grids on the spherical shells of the integration grids.[@LebedevVI_grid:1999DokladyMath] Figure \[fig:HirI\_nlebConv\]a shows the influence of the number of grid points per spherical shell on the accuracy; note the log-log scale used. In general, a denser grid results in a more accurate value for the population. However, different atoms in the same system, 