  Verstraelen et al. (J. Chem. Theory Comput. 12 (2016) 3894-3912) recently
introduced a new method for partitioning the electron density of a material
into constituent atoms. Their approach falls within the class of atomic
population analysis methods called stockholder charge partitioning methods in
which a material electron distribution is divided into overlapping atoms. The
Minimal Basis Iterative Stockholder (MBIS) method proposed by Verstraelen et
al. composes the pro-atom density as a sum of exponential functions, where the
number of exponential functions equals that element's row in the Periodic
Table. Specifically, one exponential function is used for H and He, two for Li
through Ne, three for Na through Ar, etc. In the MBIS method, the exponential
functions parameters defining the pro-atom density are optimized in a
self-consistent iterative procedure. Close examination reveals some important
anomalies in the article by Verstaelen et al. The purpose of this comment
article is to bring these important issues to readers' attention and to start a
discussion of them.
