  We report the results of an ab initio modeling of substitutional impurities
such as zinc, copper and zirconium ions incorporated into the magnesium
sublattice of MgB2. The goal of computational studies was to gain an atomistic
understanding of how the structural and bonding properties of the local ionic
environment are affected by a change in the host cation. The simulations
performed for the given set of substituents indicate that at a low doping
level, the induced lattice distortions and additional forces are noticeable
small. At the same time, the electron redistributions around the impurities
have been found to differ drastically both from that around the host cation and
from each other. Results of the first-principles calculations were used to
compare and discuss, in the context of the cation properties, specific changes
in local charge structures and in chemical bonding caused by the presence of
the impurity. Certain trends in substituent effects were found. It was
determined how the substitutional ion modifies the initial charge distribution
around the host cation position and therefore, affects both the overall picture
of the electronic states involved in the chemical bonding and the intrinsic
charge-transfer channels. The present work gives insight into structural and
electronic features of the impurity caused-processes which contribute to unique
material properties of various MgB2-solid solutions.
