I noticed that the rdf calculated by a_ri3Dc is not weighted by radius so it calculates this:

P(r) = 1/Lz 1/2pi  Int dphi dz n(r,phi,z)

not

P(r) = 1/Lz 1/2pi r Int dphi dz n(r,phi,z)

(A Ghavami via email)