Minimum-only sampling by single-component algorithm (SC-AFIR)

The SC-AFIR can also be used for automated sampling of local minimum structures. An example of input using these parameters for (H₂O)₈ clusters is:

# SC-AFIR/RHF/6-31G
 
0 1
O         -0.000000000000          0.010468354749          0.754819362610   1
H          0.000000000000          0.771670165130          1.319188188547   1
H         -0.000000000000         -0.747077150089          1.324086214974   1
O         -0.000000000000          0.010468354749          0.754819362610   2
H          0.000000000000          0.771670165130          1.319188188547   2
H         -0.000000000000         -0.747077150089          1.324086214974   2
O         -0.000000000000          0.010468354749          0.754819362610   3
H          0.000000000000          0.771670165130          1.319188188547   3
H         -0.000000000000         -0.747077150089          1.324086214974   3
O         -0.000000000000          0.010468354749          0.754819362610   4
H          0.000000000000          0.771670165130          1.319188188547   4
H         -0.000000000000         -0.747077150089          1.324086214974   4
O         -0.000000000000          0.010468354749          0.754819362610   5
H          0.000000000000          0.771670165130          1.319188188547   5
H         -0.000000000000         -0.747077150089          1.324086214974   5
O         -0.000000000000          0.010468354749          0.754819362610   6
H          0.000000000000          0.771670165130          1.319188188547   6
H         -0.000000000000         -0.747077150089          1.324086214974   6
O         -0.000000000000          0.010468354749          0.754819362610   7
H          0.000000000000          0.771670165130          1.319188188547   7
H         -0.000000000000         -0.747077150089          1.324086214974   7
O         -0.000000000000          0.010468354749          0.754819362610   8
H          0.000000000000          0.771670165130          1.319188188547   8
H         -0.000000000000         -0.747077150089          1.324086214974   8
Options
Add Interaction
Gamma=50.0
END
Temperature=500.0
rTemperature=5000.0
SCGO_NLowest=72
SCGO_PLatest=240
NRUN=24
EQOnly
DownDC=12
 

The search start from 24 random structures as specified by NRUN=24, where the mutual positions and orientations of the eight water molecules (eight parts) are randomly arranged in the 24 random structures. Although this job also calculates AFIR paths in the course of the search, the path information will not appear in main outputs because of EQOnly, i.e., xxx_TS_list.log, xxx_DC_list.log, and xxx_PT_list.log are all empty. The stopping criteria, SCGO_NLowest=72 and SCGO_PLatest=240, designate that the search will stop when the lowest energy 72 EQs are not updated by the last 240 path calculations. The lowest 72 EQs are in terms of (harmonic) free-energy at eleven different temperatures, i.e., 0, 50, 100, 150, 200, 250, 300, 350, 400, 450, and 500 K, in this case with the Temperature=500.0 keyword. The model temperature parameter T_R in the equation of μ_i (see Introduction of AFIR) is set to 5000 K by rTemperature=5000.0. The free energy values in the equation of μ_i (see Introduction of AFIR) is evaluated at T = 500ξ K in this case with the Temperature=500.0 keyword, where ξ is a random number between 0 and 1.

Frequently used options

See Global reaction route mapping by single-component algorithm (SC-AFIR).