Pair distribution function
The pair distribution function (PDF) describes the distribution of distances between pairs of particles contained within a given volume. Mathematically, if a and b are two particles in a fluid, the PDF of b with respect to a, denoted by ![g_{ab}(\vec{r})](/Images/godic/202502/01/b465ad891a03764742f80f062a6a1f8f2001.png")
is the probability of finding the particle b at the distance ![\vec{r}](/Images/godic/202502/01/fdb06cf2a399b265d4622112378c02be2001.png")
from a, with a taken as the origin of coordinates.