the atomic charges in some simple periodic systems are calculated, showing that the algorithm works correctly. Finally, in Sec. \[sc:Hir\_conclusions\] some conclusions are given.\

Methods {#sc:Hir_Methods}
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Atomic and molecular calculations {#ssc:Hir_Methods_solstatecodes}
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Hirshfeld-I calculations require CDDs as input. These can be obtained from electronic structure calculations using standard solid state or quantum chemical codes. In this work we have chosen to perform these calculations within the DFT framework using the projector augmented wave (PAW) approach for the core-valence interaction and the local density approximation (LDA) for the exchange-correlation functional as implemented in the <span style="font-variant:small-caps;">VASP</span> code.[@Blochl:prb94; @Kresse:prb99] The kinetic energy cut-off is set at $500$ eV and the $k$-point set is reduced to the $\Gamma$-point for molecular and atomic calculations. For the bulk materials sufficiently converged $k$-point sets were used. To optimize the geometry of the molecules and periodic materials a conjugate gradient algorithm is applied. For molecular calculations only the atom positions are optimized, for bulk materials the cell parameters are optimized simultaneously. All molecules are placed in periodic cells of $20.0\times 21.0\times 20.5$Å$^3$, which provide a sufficiently large vacuum region between periodic copies of the molecules, to prevent interaction.\
Hirshfeld-I data computed using the approach detailed in 