The input is a vector v containing the solute's electrostatic potential, evaluated at a set of discretization points on the cavity surface (Fig. ), while the output is a vector of surfaces charges q at the same points. These charges, {q i }, describe the polarizing effect of the medium. Several other ASC-PCM methods can be cast in the form of eq. 3, 3,10,67 and IEF-PCM is defined by a particular choice of the matrices K ε and Y ε :