Hi everyone
I pushed two molecules collision ,and I want to use RDF from center of one molecule to center of another molecule to analyze this collision process.I have read some posts about it, but I am still not sure.My first procedure is
(1)Create center for each molecule
(2)generate RDF plot

my second procedure is
(1)Create center for each molecule
(2)Define one molecule as set 1 and define another as set 2
(3)generate RDF between set 1 and set 2

I got two different plots.I am not sure which on is what I want.Please tell me the right one.

Thanks in advance 
Sincerely
Li