United-atom model

From SklogWiki
Revision as of 14:50, 17 October 2007 by Carl McBride (talk | contribs)
Jump to: navigation, search
Simeq0.png This article is a 'stub' page, it has no, or next to no, content. It is here at the moment to help form part of the structure of SklogWiki. If you add sufficient material to this article then please remove the {{Stub-general}} template from this page.

In the united-atom model the CH_2 and CH_3 units are treated as one unified interaction site (hence united-atom), i.e. the hydrogen atoms are incorporated within the carbon atoms and are not expressed explicitly. Many force fields make use of this approximation in order to reduce the computational overheads. For example, n-hexane consists of 6 carbon atoms and 14 hydrogen atoms. A fully-atomistic model of n-hexane would require 20 interaction sites. Using the united-atom approximation, this reduces to two CH_3 sites and four CH_2 sites, a significant reduction.




  1. Rolf Lustig and William A. Steele "On the thermodynamics of liquid propane", Molecular Physics 65 pp. 475-486 (1988)
  2. Sumnesh Gupta, Jia-an Yang and Neil R. Kestner "Computer modeling of liquid propane using three-site potential models", Journal of Chemical Physics 89 pp. 3733-3741 (1988)
  3. Søren Toxvaerd "Molecular dynamics calculation of the equation of state of liquid propane", Journal of Chemical Physics 91 pp. 3716-3720 (1989)
  4. Søren Toxvaerd "Molecular dynamics calculation of the equation of state of alkanes", Journal of Chemical Physics 93 pp. 4290-4295 (1990)