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tural normalization factor 

where g ( r ) is the radial distribution function (RDF). Eq. (32) is a measure of the range over which the cor- relation function decays to zero and therefore could be regarded as a correlation length of the radial distribu- tion function. The RDF (or structure factor in reciprocal 

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space) can be defined either in terms of the vector norm r$_{ij}$ between the atoms i and j or between the centres of mass of molecules i and j : g ( r ) = 〈 ∑ N i $_{=1}$∑ N j> 1 δ ( | r − r $_{ij}$| ) 4 πr $^{2}$Nρ 〉 , where N is the total number of atoms or molecules, and ρ is the atomic or molecular number density. 

The radial distribution functions and normalization factors are presented in figure 7. We can see that the RDF are typical monatomic and diatomic Lennard-Jones pair correlation functions. ξ$_{g}$ generally increases as we in- crease the density and temperature from 0 . 605 at state 

