To examine how a change in the host cation affects the structural and bonding properties of the local ionic environment, we have performed a series of ab initio simulations of substitutional impurities such as zinc, copper, and zirconium ions incorporated into the magnesium sublattice of MgB2. It was shown that at a low doping level, the induced lattice distortions and additional forces are noticeable small. For the given set of substituents, it was also determined how the impurity 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. In the context of the cation properties, by analyzing specific changes in local charge structures caused by the presence of the impurity, the existence of two different trends in the Mg-site substitution effect was found and discussed. © 2012 Wiley Periodicals, Inc.