with the particle density of type
at a distance around particles , and
the particle density of type
averaged over all spheres around particles with
radius (see Fig. 52 C).
Usually the value of is half of the box length. The
averaging is also performed in time. In practice the analysis program
gmx rdf divides the system
into spherical slices (from to , see
Fig. 52 A) and makes a histogram in stead of
the -function. An example of the RDF of oxygen-oxygen in
SPC water 80 is given in Fig. 53
With gmx rdf it is also possible to calculate an angle
dependent rdf , where the angle
is defined with respect to a certain laboratory axis ,
see Fig. 52 B.
This is useful for analyzing anisotropic
systems. Note that in this case the normalization
is the average density in
all angle slices from to up to
, so angle dependent, see Fig. 52 D.