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

computational chemistry Computational chemistry is a branch of chemistry that uses computer simulations to assist in solving chemical problems. It uses methods of theoretical chemistry incorporated into computer programs to calculate the structures and properties of mol ...

to model

solvation Solvations describes the interaction of a solvent with dissolved molecules. Both ionized and uncharged molecules interact strongly with a solvent, and the strength and nature of this interaction influence many properties of the solute, includi ...

effects. When it is necessary to consider each

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

molecule A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...

as a separate molecule, the computational cost of modeling a solvent-mediated

chemical reaction A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...

becomes prohibitively high. Modeling the solvent as a polarizable continuum, rather than individual molecules, makes ''

ab initio ( ) is a Latin term meaning "from the beginning" and is derived from the Latin ("from") + , ablative singular of ("beginning"). Etymology , from Latin, literally "from the beginning", from ablative case of "entrance", "beginning", related t ...

'' computation more readily achievable. Two types of PCMs have been popularly used: the dielectric PCM (D-PCM), in which the continuum is polarizable (see

dielectrics In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the materia ...

), and the conductor-like PCM (C-PCM), in which the continuum is conductor-like, similar to the

COSMO Solvation Model COSMO (COnductor-like Screening MOdel) is a calculation method for determining the electrostatic interaction of a molecule with a solvent. COSMO is a dielectric continuum model (a.k.a. continuum solvation model). These models can be used in compu ...

.Jacopo Tomasi, Benedetta Mennucci, and Roberto Cammi (2005). "Quantum Mechanical Continuum Solvation Models." Chem. Rev. 105(8): 2999-309

/ref> The molecular Gibbs free energy, free energy 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 The Charge-transfer 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 (DFT) is a computational quantum mechanical modelling method used in physics, chemistry and materials science to investigate the electronic structure (or nuclear structure) (principally the ground state) of many-body ...

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

Gaussian Carl Friedrich Gauss (1777–1855) is the eponym of all of the topics listed below. There are over 100 topics all named after this German mathematician and scientist, all in the fields of mathematics, physics, and astronomy. The English eponymo ...

, GAMESS an
JDFTx
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 is a cycloalkane with the molecular formula . Cyclohexane is non-polar. Cyclohexane is a colourless, flammable liquid with a distinctive detergent-like odor, reminiscent of cleaning products (in which it is sometimes used). Cyclohexan ...

acetone Acetone (2-propanone or dimethyl ketone) is an organic compound with the chemical formula, formula . It is the simplest and smallest ketone (). It is a colorless, highly Volatile organic compound, volatile, and flammable liquid with a charact ...

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

, and

acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not class ...

electrostatic effects are dominant while in

carbon tetrachloride Carbon tetrachloride, also known by many other names (such as carbon tet for short and tetrachloromethane, also IUPAC nomenclature of inorganic chemistry, recognised by the IUPAC), is a chemical compound with the chemical formula CCl4. It is a n ...

benzene Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...

, and

chloroform Chloroform, or trichloromethane (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...

other nonelectrostatic effects are more important." There is an

integral equation In mathematical analysis, integral equations are equations in which an unknown function appears under an integral sign. In mathematical notation, integral equations may thus be expressed as being of the form: f(x_1,x_2,x_3,\ldots,x_n ; u(x_1,x_2 ...

formalism (IEF) version of the PCM which is very commonly used. PCM is also used to model outer solvation layers in multi-layered solvation approach.Mark S. Gordon "CLUSTER-BASED APPROACHES TO SOLVATION" Iowa State University, Ames Laborator

References

{{reflist Computational chemistry

See also

References