Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The polarizable continuum model (PCM) is a commonly used method in computational chemistry to model solvation effects. If it were necessary to consider each solvent molecule as a separate molecule, the computational cost of modeling a solvent-mediated chemical reaction would grow prohibitively high. Modeling the solvent as a polarizable continuum, and not as individual molecules, makes ab initio computation feasible. Two types of PCMs have been popularly used: dielectric PCM (D-PCM) which deals the continuum as a polarizable dielectrics and conductor-like PCM (C-PCM) which deals the continuum as a conductor-like picture similar to COSMO Solvation Model.