Sir,
I am trying to implement hybrid potential for nanocomposite. The nanocomposite is having Boron nitride (BN) as nanotube and epoxy as matrix. I am using extep (extended Tersoff) for BN and PCFF for polymer as my potential. But when i am running the simulation its giving an error “Pair coeff for hybrid has invalid style”. When I run the simulation alone for both, Its working fine. I have also checked the manual and lammps directory for sorting it out but didn’t found solution to this. I also searched on lammps forum and found same type of query but the solution is missing. I am using Lammps 64-bit 19 sep 2019.
I am attaching my input file and data file with this mail. Please help me that how to implement hybrid potential for my simulation. Thanking you in advance.
Data file:
1.in (2.09 KB)
BN55_450Ph_470CH2_4.data (676 KB)
your last pair_coeff line is incorrect in multiple ways. please study the pair style hybrid documentation carefully to see how to fix that issue.
axel.
…and you are going to have a second problem: there are no interactions defined between the two sets of atom types with the different pair styles.
Sir,
I have read the lammps document again and modified my input script for the pair_coeff of B & N as:
pair_coeff 6 6 extep BN.extep B NULL
pair_coeff 7 7 extep BN.extep NULL N
And the interaction between all the atom types defined with lj/cut 3.0.
But the error still persist the same as incorrect args for pair coefficients.
I also searched lammps forum so much but didn’t find solution to this type of potential.
It will be great favor for me if you help me with the solution.
Sir,
I have read the lammps document again and modified my input script for the pair_coeff of B & N as:
you may have read it, but you don’t understand it.
pair_coeff 6 6 extep BN.extep B NULL
pair_coeff 7 7 extep BN.extep NULL N
both of these lines are very obviously incorrect and in violation of what the documentation requires.
And the interaction between all the atom types defined with lj/cut 3.0.
a cutoff of 3.0 angstrom for lennard jones with metal units makes no sense.
But the error still persist the same as incorrect args for pair coefficients.
yes, because they are incorrect.
I also searched lammps forum so much but didn’t find solution to this type of potential.
It will be great favor for me if you help me with the solution.
the solution is to correctly follow the documentation, not just pick something random.
you are not understanding how a hybrid pair style works and how manybody pair styles work and what their limitations are. your understanding is so far away from what is reasonable and meaningful, that I don’t know how to explain what you need to do.
axel.
Sir,
I read the lammps document again but not able to find out what’s the problem is. When I seperated the BN from the polymer data and run the simulation, its running smoothly. I know your time is precious but there is no any example available for implementing hybrid potential for class 2 and extep. If you help with this there will be one example from where people can understand how to implement class 2 and extep together in hybrid. I am again apologizing for wasting your time.
You have to do better than just looking for examples and for your specific case only. There are explanations and examples for other manybody potentials where the same rules and requirements apply. As I mentioned before, you need to gain a better understanding in how things work in general in LAMMPS or we will have the same conversation over and over again, if you cannot figure out this simple issue.
Axel
Sir,
Thanks for your help. I modify my input script and now I am not getting the previous error “incorrect args for pair coefficients” for hybrid pair_style but now I am getting a new error that “All pair_coeff are not set”. I understand that the error is due to missing of some pair_coeff for some atom type. But, in my input script I have already described the pair_coeff for every types of atoms. I need your help again because I am not able to figure out where I am making mistake again.
I am attaching my new input script with this mail.
Please help me.
1.in (2.73 KB)
If your force field has cross terms, then “All pair_coeff are not set” could be referring to that.
Will
please use the “info coeffs” command before the “run” command. it will tell you exactly for which pairs of types there are no settings.
please note, that with hybrid pair styles, certain combinations cannot be auto-generated with mixing rules.
axel.
Sorry but I didn’t understand what you are referring to. I already have defined pair_coeff for all same atom types as well as all different atom types. I even defined pair_coeff for all interactions. Then, where i am lagging? Sir, it will be more helpfull for me if you elaborate a little bit.
Okay sir. I will do. Thanks again for your kind help.
you have another (big) problem:
the extep parameter file has settings for “metal” units, but your input requests “real” units.
this will render the “extep” part bogus.
axel.