The $svp section is available to specify special parameters to the solvation module such as cavity grid parameters and modifications to the numerical integration procedure. The $svpirf section allows the user to specify an initial guess for the solution of the cavity charges. As discussed in section 12.2.5, the $svp and $svpirf input sections are used to specify parameters for the iso-density implementation of SS(V)PE. An alternative implementation of the SS(V)PE mode, based on a more empirical definition of the solute cavity, is available in the PCM (see Section 12.2.2) and controlled from within the $pcm input section.