Another useful algorithm termed DS-AFIR is available in GRRM17. DS-AFIR can find a single path linking two given structures. It can also be applied to multistep paths that have more than one TS. Like the other double-end methods, the obtained path does not necessarily correspond to the kinetically most preferable one but to the shortest one, when multiple paths exist between given end points. For details about its theoretical background, see S. Maeda, et al., J. Comput. Chem., 2018, 39, 233–251. (this paper is Open Access).
An input file for formaldehyde is:
C -0.000000000711 0.000000000452 -0.533622543616
O 0.000000000233 0.000000000201 0.679217381431
H 0.000000000239 0.942015259527 -1.124391918573
H 0.000000000239 -0.942015260180 -1.124391919242
C -0.059812606249 -0.089247148224 -1.464752471288
O 0.281184347657 0.091182904031 -0.045324134110
H 0.282312601899 0.963830397357 0.435556525764
H 0.545483152071 -0.641273618364 0.576228105743
A DS-AFIR calculation gives xxx_EQ_list.log, xxx_TS_list.log, and xxx_PT_list.log in the same format to those the SC-AFIR calculation gives. The RePATH can also be applied, to find TSs along these paths with a different computational level or to automatically recover TSs that are missed in the initial application (if any).