---
abstract: 'In this work, a method is described to extend the iterative Hirshfeld-I method, generally used for molecules, to periodic systems. The implementation makes use of precalculated pseudo-potential based charge density distributions, and it is shown that high quality results are obtained for both molecules and solids, such as ceria, diamond, and graphite. The use of such grids makes the implementation independent of the solid state or quantum chemical code used for studying the system. The extension described here allows for easy calculation of atomic charges and charge transfer in periodic and bulk systems.'
author:
- 'D. E. P. Vanpoucke'
- 'P. Bultinck'
- 'I. Van Driessche'
bibliography:
- 'danny.bib'
- 'Hirshfeld.bib'
- 'notes.bib'
title: 'Extending Hirshfeld-I to bulk and periodic materials.'
---

Introduction
============

One of the most successful concepts in chemistry is that of “atoms in molecules” (AIM). It states that the properties of a molecule can be seen as simple sums of the properties of its constituent atoms. An impressive amount of insights has been obtained from such a viewpoint, although a precise definition of an AIM remains elusive.[@AyersPW:2000JCP; @BaderRFWMattaCF:2004JPhysChemA; @BaderRFWMattaCF:2006JPhysChemA] All AIM methods have the common purpose of trying to improve our understanding of chemical 