presented Hirshfeld results for metal–organic frameworks using the DDEC-code of Manz and Sholl.[@ManzSholl:JChemTheoryComp2010] The same code was probably also used in the investigation of charge injection in graphene layers by Rogers and Liu.[@RogersGWLiuJZ:JACS] These authors present Hirshfeld-I charges, though they do not mention explicitly how these were obtained.\
It is clear that there is a growing interest in codes that can provide atomic populations, however, only few true bulk systems have been investigated using a purely atom based Hirshfeld-I method. For this reason most numerical tests in this work are performed on molecules, though we will investigate the behavior of periodic systems at the end of this section. As a first test system we have chosen the CO molecule. Its small size makes it easily suitable for quick test calculations, and its heteronuclear structure should result in a non-zero charge transfer, at least at equilibrium distance.\
Before proceeding, the different grids used in our current setup of the Hirshfeld-I scheme for periodic systems are introduced. In this setup there are two ‘types’ of CDDs: that of the system and that of the free atoms/ions, which are indicated in the following as the subscripts ‘$sys$’ and ‘$atom$’, respectively. In this, ‘system’ 