My model consists of hydroxylated silica as the bottom layer from bottom to top C12H26、 Water layer and supercritical CO2, the bottom layers of the two models are exactly the same, the difference is that one has a single layer of graphene added at the top, while the other does not. The overall model is under the NPT ensemble, and the PPP boundary conditions are all based on the Reaxff force field,
If there is no successful operation without adding a graphene layer, starting again with a graphene layer will result in an error:
ERROR: Incorrect args for pair coefficients (src/REAXFF/pair_reaxff.cpp:280)
Last command: pair_coeff * * reaxff CHONSSIX.reax O Si H C C H O C O
Please read the forum guidelines to learn how to properly report such issues and specifically which information to provide. Specifically, a vague description of the contents of your input is rather useless when discussing errors.
Due to lack of information I can only say, that you obviously have a syntax error in your input and that you have to resolve it by following the documentation for the pair_coeff and pair_style reaxff commands.
From your username, I guess you’re in a similar position to mine. If you want to get started with the ReaxFF force field basics, I recommend the Bilibili video BV1Mb4y1b7a5.
Additionally, when asking questions, it’s best to provide the complete input files and full error messages. I’ve pasted the pair_coeff syntax in the next comment/part below.
Only a single pair_coeff command is used with the reaxff style which specifies a ReaxFF potential file with parameters for all needed elements. These are mapped to LAMMPS atom types by specifying N additional arguments after the filename in the pair_coeff command, where N is the number of LAMMPS atom types:
- filename
- N indices = ReaxFF elements
The filename is the ReaxFF potential file.
In the ReaxFF potential file, near the top, after the general parameters, is the atomic parameters section that contains element names, each with a couple dozen numeric parameters. If there are M elements specified in the ffield file, think of these as numbered 1 to M. Each of the N indices you specify for the N atom types of LAMMPS atoms must be an integer from 1 to M. Atoms with LAMMPS type 1 will be mapped to whatever element you specify as the first index value, etc. If a mapping value is specified as NULL, the mapping is not performed. This can be used when the reaxff style is used as part of the hybrid pair style. The NULL values are placeholders for atom types that will be used with other potentials.
As an example, say your LAMMPS simulation has 4 atom types and the elements are ordered as C, H, O, N in the ffield file. If you want the LAMMPS atom type 1 and 2 to be C, type 3 to be N, and type 4 to be H, you would use the following pair_coeff command:
pair_coeff * * ffield.reax C C N H