Fork of PCBM Tris (the 120'deg spaced flat one, TTT4), from
https://github.com/jarvist/CoarseGrainPCBM/blob/master/2013-01_CG_fit_to_atomistic_workings/tris_isomer_mix/TRIS-PCBM-ISOMERS.top
Basic imports from previous work:
https://github.com/jarvist/CoarseGrainPCBM/tree/master/2013-01_CG_fit_to_atomistic_workings/tris_isomer_mix