Format of the trainset.in file for parameterization
For each structure that is referred to in the trainset.in file, there must be a corresponding entry in the geo file. The format of several sections in the trainset.in file is shown below (taken from ~jkua/reac/sbcl/trainset.in)
First a definition: The match criteria is how close you want ReaxFF to try to match the quantum mechanics (QM) data.
Second, here's the geometry part of the structure (SbCl3) from the geo file for reference. Most importantly, Sb is atom #1, and atoms #2-#4 are Cl.
HETATM 1 Sb 40.41155 39.64213 39.99990 Sb 1 1 0.00000
HETATM 2 Cl 38.84005 39.61667 41.82186 Cl 1 1 0.00000
HETATM 3 Cl 40.90611 41.99579 40.00002 Cl 1 1 0.00000
HETATM 4 Cl 38.84041 39.61663 38.17845 Cl 1 1 0.00000
Now on to the three sections: CHARGE, GEOMETRY, ENERGY.
CHARGES
sbcl3_24.op 0.05 1 0.6671
sbcl3_24.op 0.05 2 -0.2222
ENDCHARGES
The CHARGE Section has four columns. The first column has the DESCRP corresponding to the structure in geo. The second column is the match criteria. For charges, you want to be within 0.05 units of the QM value. The third column is the atom number. If you look at the geo file, you'll see that 1 is Sb and 2 is Cl. The fourth column is the QM data, i.e., the charge on Sb is +0.6671. The charges on the Cl are -0.2222 each. You could also put in the charges for the other two Cl atoms (3 and 4) but they would all be about the same.
GEOMETRY
sbcl3_24.op 0.02 2 1 2.4057
sbcl3_24.op 0.02 3 1 2.4057
sbcl3_24.op 0.02 4 1 2.4057
sbcl3_24.op 2.0 3 1 2 98.3258
sbcl3_24.op 2.0 4 1 3 98.3258
sbcl3_24.op 4.0 4 1 3 2 99.8714
ENDGEOMETRY
The GEOMETRY section...
ENERGY
# SbCl2 + Cl --> SbCl3
10.0 + sbcl3_18/1 - sbcl2_24.op/1 - cl_mu2/1 41.86
3.0 + sbcl3_20/1 - sbcl2_24.op/1 - cl_mu2/1 -31.67
1.0 + sbcl3_22/1 - sbcl2_24.op/1 - cl_mu2/1 -49.09
1.0 + sbcl3_24.op/1 - sbcl2_24.op/1 - cl_mu2/1 -65.43
1.0 + sbcl3_26/1 - sbcl2_24.op/1 - cl_mu2/1 -61.78
2.0 + sbcl3_28/1 - sbcl2_24.op/1 - cl_mu2/1 -53.92
2.0 + sbcl3_30/1 - sbcl2_24.op/1 - cl_mu2/1 -44.72
2.0 + sbcl3_32/1 - sbcl2_24.op/1 - cl_mu2/1 -35.54
5.0 + sbcl3_34/1 - sbcl2_24.op/1 - cl_mu2/1 -27.10
5.0 + sbcl3_36/1 - sbcl2_24.op/1 - cl_mu2/1 -19.64
5.0 + sbcl3_38/1 - sbcl2_24.op/1 - cl_mu2/1 -13.20
5.0 + sbcl3_40/1 - sbcl2_24.op/1 - cl_mu2/1 -7.77
5.0 + sbcl3_42/1 - sbcl2_24.op/1 - cl_mu2/1 -3.11
5.0 + sbcl3_44/1 - sbcl2_24.op/1 - cl_mu2/1 -0.31
# SbCl3 + Cl --> SbCl4
15.0 + sbcl4_24.op/1 - sbcl3_24.op/1 - cl_mu2/1 -16.91
ENDENERGY