SMx family of solvation models

The basic equations of the SMx models follow. The standard-state free energy 

The electrostatic contribution (G/aq)) is modeled by the generalized Bom approximation [49] with atom-centered charges and with the effects of dielectric descreening by other parts of the solute calculated from a conformationally sensitive solute shape molecular model [50-53] based on overlapping atomic spheres. It leads to the following equation  

In this case, Y/tt is a coulomb integral, and and are the net atomic partial charges AGp is the electric polarization part of the free energy of solvation. 

The NDDO approximation of the Hartree-Fock equation for the SMx models can be written as follows  

The last term in equation 17, which is required for accurate calculations of the absolute free energies of solvation, is modified differently for various SMx models. For example, in SM2 and SM3 versions it has the following form 

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