Stockmayer potential

{{Short description|Model of atomic and molecular potential energy}}

File:Stockmayerpotential.svg

The Stockmayer potential is a mathematical model for representing the interactions between pairs of atoms or molecules. It is defined as a Lennard-Jones potential with a point electric dipole moment.

A Stockmayer liquid consists of a collection of spheres with point dipoles embedded at the centre of each. These spheres

interact both by Lennard-Jones and dipolar interactions. In the absence of the point dipoles, the spheres face no rotational

friction and the translational dynamics of such LJ spheres have been studied in detail. This system, therefore, provides

a simple model where the only source of rotational friction is dipolar interactions.{{citation|periodical=Chem. Soc. Rev.|title=Solvation dynamics in dipolar liquids|volume=39|issue=6|pages=1936–1954|date= 2010|language=German|doi=10.1039/b902048a

|pmid=20502796|last1=Bagchi|first1=Biman|last2=Jana|first2=Biman}}

The interaction potential may be written as

$V(r)\; =\; 4\; \backslash varepsilon\_\{12\}\backslash left[\backslash left(\backslash frac\{\backslash sigma\_\{12\}\}\{r\}\backslash right)^\{12\}\; -\; \backslash left(\backslash frac\{\backslash sigma\; \_\{12\}\}\{r\}\backslash right)^\{6\}\backslash right]$

- \xi \left(\frac{\mu _1 \mu _2}{r^3}\right)

where the parameters $\backslash varepsilon\_\{12\}$ and $\backslash sigma\_\{12\}$ are related to dispersion strength and particle size respectively, just as in the Mie potential or Lennard-Jones potential, which is the source of the first term, $\backslash mu\_i$ is the dipole moment of species $i$, and $\backslash xi$ is a parameter describing the relative orientation of the two dipoles, which may vary between -2 and 2.{{Cite journal |last=Mason |first=E. A. |last2=Monchick |first2=L. |date=1962-05-15 |title=Transport Properties of Polar-Gas Mixtures |url=https://pubs.aip.org/jcp/article/36/10/2746/76512/Transport-Properties-of-Polar-Gas-Mixtures |journal=The Journal of Chemical Physics |language=en |volume=36 |issue=10 |pages=2746–2757 |doi=10.1063/1.1732363 |issn=0021-9606|url-access=subscription }}