SPC/E water potential implementation

I used your spc/e code and data file and ran both.

I then used your data file in my code ( using your parameters),
and got identical output values. So the code is ok.

The “nan” error was from overlapping water molecules I created randomly; ( somehow, the same random
data worked when pair_coeff * * was non zero ).

No “nan” error occurred, when I created water molecules on a uniform grid without overlap.

Thanks again for the spc/e bench mark link.

regards
shankar