region accurately. The number of radial points was chosen to equal the numbers suggested by Becke.[@BeckeAD:1987JCP] At each point in this radial grid grid, a shell is located on which grid points are distributed according to a Lebedev-Laikov grid.[@LebedevVI_grid:1999DokladyMath] (*cf.* Sec. \[ssc:sphereIntgrid\]) The total number of grid points $S$ equals the sum over all atoms of the number of radial points ($R_{A}$) used for that atom times the number of points on each shell ($\sigma$): $S=\sum_{A}{R_{A}\cdot\sigma}$. In the remainder only $\sigma$ is varied to study the stability of the integrations. Two three-dimensional spherical grids are distinguished:

    -   S$_{atom}$ : Total spherical grid used to generate the reference spherically averaged radial density distribution for the atoms.

    -   S$_{sys}$ : The multi-center spherical grid for the system under study.

Note that the results of the Hirshfeld-I AIM analysis depend directly on $S_{sys}$ but also indirectly on $S_{atom}$ as this determines the quality of the isolated atomic CCDs.

![The Hirshfeld-I charge for the C atom in a CO molecule as function of the V$_{sys}$ grid resolution. The different curves show the results for the use of different resolutions in the V$_{atom}$ grids, used for generating the atomic radial densities. In all molecular calculations 