Dear Byung-Hyun Kim,
There is no Si-C bond defined in parameter set of Reax.
Because of that you are having such an error: unknown bond in molecule.
You may use Si-C bond parameters in the previous version of ReaxFF but I recommend using after valid tests:
bond parameters
1 6 108.3910 95.0233 0.0000 0.1129 -0.5558 1.0000 17.2117 0.4568
0.2424 -0.2378 10.1163 1.0000 -0.1020 5.7156 1.0000 0.0000
off diagonal parameters
1 6 0.0541 2.0811 13.5179 1.7778 1.5840 -1.0000
angle parameters
1 1 6 72.5239 22.3583 2.0393 0.0000 1.0031 0.0000 1.0400
1 6 1 69.1709 18.9268 2.1226 0.0000 1.0031 0.0000 1.0400
6 1 6 68.6453 18.7377 2.0496 0.0000 1.0031 0.0000 1.0400
1 6 6 68.9902 19.7021 2.0587 0.0000 1.0031 0.0000 1.0400
2 1 6 72.6403 13.6964 2.4702 0.0000 1.0000 0.0000 1.0400
1 6 2 71.8708 14.6864 2.4702 0.0000 1.0000 0.0000 1.0400
1 3 6 85.8521 12.6881 1.0112 0.0000 1.0000 0.0000 1.3220
1 6 3 71.7524 35.8987 1.5000 0.0000 1.0000 0.0000 1.0487
3 1 6 70.0000 5.0250 1.0000 0.0000 1.0000 0.0000 1.2500
1 2 6 0.0000 2.5000 1.0000 0.0000 1.0000 0.0000 1.2500
if you add previous lines in the appropriate places in ffield.reax file
you may use Reax for Si-C systems.
DUNDAR YILMAZ
Phd Candidate
Bilkent University Dept. of Physics
[email protected]...