Physical interpretation of pair distribution functions

Kirkwood brilliantly realized that fiquids are not completely random distributions of atoms in volume V (Fig. 9.1). Instead fiquids possess 

In the previous section, we found that the joint probability of finding 

This can be expressed in terms of the pairwise distribution function as follows  

This means that the average number of particles at position 2 to L2 + dr 2 provided that there is a particle at position rj to Li + dr, is 

PgfiLi, L2)dLn-In other words, the expected local density around a particle is 

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