polyene/alkane/PAH test systems: polyenes.xyz, alkane.xyz, PHAs.extxyz,
BDE data derived from QM9:
"all_frags_all_prop.extxyz" is all radicals that has been successfully optimized
"cleave_pos_record.pickle" records the potential dissociable bond/atom-pairs in QM9 molecules
"all_frags_rec.pickle" records the indices of fragments generated according to the bond dissociation reaction in "cleave_pos_record.pickle"(* note that they are not all effective*)
"effective_ids.npy" effective fragments indices, a bond dissociation reaction is effective only if both fragments are in it.