The polarizable continuum model (PCM) is a commonly used method in computational chemistry

Computational chemistry

Computational chemistry is a branch of chemistry that uses principles of computer science to assist in solving chemical problems. It uses the results of theoretical chemistry, incorporated into efficient computer programs, to calculate the structures and properties of molecules and solids...

 to model solvation

Solvation

Solvation, also sometimes called dissolution, is the process of attraction and association of molecules of a solvent with molecules or ions of a solute...

 effects. If it were necessary to consider each solvent molecule as a separate molecule, the computational cost of modeling a solvent-mediated chemical reaction

Chemical reaction

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

 would grow prohibitively high. Modeling the solvent as a polarizable continuum, and not as individual molecules, makes ab initio

Ab initio

ab initio is a Latin term used in English, meaning from the beginning.ab initio may also refer to:* Ab Initio , a leading ETL Tool Software Company in the field of Data Warehousing.* ab initio quantum chemistry methods...

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

COSMO Solvation Model

COSMO is the abbreviation for "COnductor-like Screening MOdel", a calculation method for determining the electrostatic interaction of a molecule with a solvent....

.

The molecular free energy

Gibbs free energy

In thermodynamics, the Gibbs free energy is a thermodynamic potential that measures the "useful" or process-initiating work obtainable from a thermodynamic system at a constant temperature and pressure...

 of solvation is computed as the sum of three terms:

G_sol = G_es + G_dr + G_cav

G_es = electrostatic

G_dr = dispersion-repulsion

G_cav = cavitation

Charge-transfer

Charge-transfer

Charge-transfer may refer to:* Intervalence charge transfer* Charge-transfer complex* Charge-exchange ionization, a form of gas phase ionization...

 effect is also considered as a part of solvation in cases.

The PCM solvation model is available for calculating energies and gradients at the Hartree–Fock and density functional theory

Density functional theory

Density functional theory is a quantum mechanical modelling method used in physics and chemistry to investigate the electronic structure of many-body systems, in particular atoms, molecules, and the condensed phases. With this theory, the properties of a many-electron system can be determined by...

 (DFT) levels in several quantum chemical computational packages such as GAUSSIAN

GAUSSIAN

Gaussian is a computational chemistry software program initially released in 1970 by John Pople and his research group at Carnegie-Mellon University as Gaussian 70. It has been continuously updated since then...

 and GAMESS

GAMESS

GAMESS is a computational chemistry software program and stands for General Atomic and Molecular Electronic Structure System. The original code of GAMESS split in 1981 and now the three version differ considerably:* GAMESS * GAMESS * PC GAMESS...

.

The authors of a 2002 paper observe that PCM has limitations where non-electrostatic effects dominate the solute-solvent interactions. They write in the abstract: "Since only electrostatic solute-solvent interactions are included in the PCM, our results lead to the conclusion that, for the seven molecules studied, in cyclohexane

Cyclohexane

Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which being intermediates used in the production of nylon...

, acetone

Acetone

Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...

, methanol

Methanol

Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

, and acetonitrile

Acetonitrile

Acetonitrile is the chemical compound with formula . This colourless liquid is the simplest organic nitrile. It is produced mainly as a byproduct of acrylonitrile manufacture...

 electrostatic effects are dominant while in carbon tetrachloride

Carbon tetrachloride

Carbon tetrachloride, also known by many other names is the organic compound with the formula CCl4. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, and as a cleaning agent...

, benzene

Benzene

Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

, and chloroform

Chloroform

Chloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes. The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous...

other nonelectrostatic effects are more important."

There is an integral equation formalism (IEF) version of the PCM (ref. 4 in the 2002 paper).

PCM is also used to model outer solvation layers in multi-layered solvation approach.