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Gasteiger-Marsili

Calculation of atom partial charges (Gasteiger-Marsili) [gm78]. The Partial Equalization of Orbital Electronegativities (PEOE) sigma charges of atoms can be calculated using an iterative algorithm. There exists a dependency between the electronegativity and the charge qA of an atom:

Equation 1. Orbital electronegativity based on atom charge

where i is the orbital and A the atom.

The algorithm requires the polynomial coefficients ai, bi, ci the damping factor and the maximal number of iterations Nmax. Because the amount of charge transferred at each iteration is damped with an exponentially decreasing factor the convergence is guaranteed.