Hello everyone, I have build the polymer system in Material studio. My MD system consists of C. H, O, N elements. Previously , I used the PCFF forcefield and converted to DATA file readable in LAMMPS which include information as:
Masses
Pair Coeffs # lj/class2/coul/long
Bond Coeffs # class2
Angle Coeffs # class2
Dihedral Coeffs # class2
Improper Coeffs # class2
...
Atoms type, XYZ position etc.
I want to use ReaxFF force field now. Is it sufficient to input the Atom types, XYZ position as DATA file in LAMMPS? Use of Pair style reax/c. Is there anything which I should concern about?
The data file contains basic information about the initial atomic coordinates, molecular topology, and (optionally) force-field coefficients.
The pair style reax performs a charge equilibration (QEq) calculation and pair style reax/c computes the ReaxFF potential of van Duin and Goddard.
The ReaxFF parameter files provided were created using a charge equilibration (QEq) model for handling the electrostatic interactions. Therefore, by default, LAMMPS requires that the fix qeq/reax command be used with pair_style reax/c when simulating a ReaxFF model, to equilibrate charge each timestep.
For more technical details about the pair reax/c implementation of ReaxFF, please check out Adri Van Duin's group homepage.
Also, you need a set of potential parameters for the reactive force field. Standard parameter sets are already included in LAMMPS. For better accuracy or special material systems, you have to generate your own parameter set which is not trivial. But you can find adapted parameter sets or buy at http://www.reaxff.com.
You can following this link
https://www.researchgate.net/deref/http%3A%2F%2Fwww.reaxff.com
Thanks @Seyedeh Tahereh Hosseini & Abdelkader Dehbi for your help. But @Abdelkader Dehbi link is not working. But its fine. I have learned to create data file for ReaxFF :-).
After installation of LAMMPS in PC, Check it "C:\Program Files\LAMMPS 64-bit 15Apr2020-MPI\Examples\reax\RDX". It helps a lot for beginner.
Hello Ankit,
I am in the same situation you were in before, I am trying to module polyurea. Could you share how you created the data field for ReaxFF?
Hello @ Carlos Gamez, To have a data file, I was using msi2lmp tool available in LAMMPS.
The msi2lmp is useful to create the data file even in the case of using the reaxff force field. Reaxff does not need connectivity informations in the data file as lammps determine such information during the MD simulation. The data file can be constructed with some other programs (see https://www.researchgate.net/post/Is-there-a-free-software-to-prepare-LAMMPS-input-file). I frequently use
ovito (https://www.ovito.org), atomsk (https://atomsk.univ-lille.fr/) or lammps_interface (https://github.com/peteboyd/lammps_interface).
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