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The Electronegativity Equalization Method (EEM) is a fast approach for chargecalculation. A challenging part of the EEM is the parameterization, which is performedusing ab initio charges obtained for a set of molecules. The goal of our work was to performthe EEM parameterization for selected sets of organic, organohalogen and organometalmolecules. We have performed the most robust parameterization published so far. The EEMparameterization was based on 12 training sets selected from a database of predicted 3Dstructures (NCI DIS) and from a database of crystallographic structures (CSD). Each setcontained from 2000 to 6000 molecules. We have shown that the number of molecules inthe training set is very important for quality of the parameters. We have improved EEMparameters (STO-3G MPA charges) for elements that were already parameterized,specifically: C, O, N, H, S, F and Cl. The new parameters provide more accurate chargesthan those published previously. We have also developed new parameters for elements thatwere not parameterized yet, specifically for Br, I, Fe and Zn. We have also performedcrossover validation of all obtained parameters using all training sets that included relevantelements and confirmed that calculated parameters provide accurate charges. |
