Hi everyone,

       I'm trying to take some Forcite results and find the orientational correlation for a polyethylene chain as a function of simulation time and distance. I want to use

the spatial orientation correlation function.But I donnot know how to define two sets and the relation beween the two sets?I want to know the C-C bond
orientation along the polyethylene chain or x-axis?How can I do?I read a paper and the author draw a plot as below.

Thanks.