United-atom model: Difference between revisions

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In the '''united-atom model''' the <math>CH_2</math> and <math>CH_3</math> units
In the '''united-atom model''' the <math>CH_2</math> and <math>CH_3</math> units
are treated as one point, i.e. the hydrogen atoms are incorporated within  
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]]
the carbon atoms and are not expressed explicitly. Many [[force fields]]
make use of this approximation in order to reduce the computational  
make use of this approximation in order to reduce the computational  

Revision as of 18:22, 21 August 2007

In the united-atom model the and 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 sites and four sites, a significant reduction.

Justification

Parameters

References