Charge Equilibration Based on Atomic Ionization in Metal–Organic Frameworks

In this article,
two new charge equilibration methods for estimating
atomic partial charges are outlined. These methods are based on expanding
the Taylor series used to estimate the ionization energy of each atom
about either the formal or atomic charge, allowing for accurate charge
estimation in both covalent and ionic materials. A new treatment of
hydrogen atoms based on molecular hydrogen is also introduced. To
demonstrate their general applicability, these new methods have been
applied to the simulation of CO2 adsorption in metal–organic
frameworks. Comparisons with other charge equilibration methods and
density functional theory (DFT) calculations show that, of the rapid
charge-assigning methods, the algorithm based on atomic ionization
best replicates the DFT electrostatic potential and provides the most
accurate estimation of CO2 adsorption.