Computing Nickel lattice parameter using ReaxFF force field

Dear Lammps Users,

I am trying to carry out some MD simulations on Nickel using ReaxFF force field. As a starting point, I tried to compute the lattice parameter for Nickel using the input script in LAMMPS tutorial section. For potential, I imported a file from ADF software. My input script is as follows:

clear
units real
dimension 3
boundary p p p
atom_style charge
atom_modify map array
lattice fcc 3.52 #lattice parameter for Ni
region box block 0 1 0 1 0 1 units lattice
create_box 1 box

lattice fcc 3.52 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1
create_atoms 1 box
replicate 1 1 1
pair_style reax/c NULL checkqeq no
pair_coeff * * ffield.reax.CHONSFPtClNi Ni
neighbor 2. bin
neigh_modify every 5 delay 0 check yes
fix 1 all qeq/reax 1 0.0 10.0 1e-6 reax/c

Dear Lammps Users,

I am trying to carry out some MD simulations on Nickel using ReaxFF force field. As a starting point, I tried to compute the lattice parameter for Nickel using the input script in LAMMPS tutorial section. For potential, I imported a file from ADF software. My input script is as follows:

##########################################################
The problem is my simulation ended up to the following Warning without reaching to the end of simulation:
"WARNING: Proc sub-domain size < neighbor skin, could lead to lost atoms (…/domain.cpp:933)"

your system is TINY for a classical MD code (hence the warning), and i doubt the ReaxFF code is set up to handle this kind of system with few real and many ghost atoms properly.

set up a larger box (like 10x10x10) and see, if that works better.

axel.

Dear Dr.Kohlmeyer,

Thank you for your response. I used another ReaxFF force field file imported from ADF software, and this time my simulation has been ended without warning. I compared the Ni atom parameters in two force field and I noticed that some of them are different. Do you think that maybe some of force field files from ADF software could not be compatible with LAMMPS. I am asking this because both potential files work fine in ADF.

Regards,

Shahin

Dear Dr.Kohlmeyer,

Thank you for your response. I used another ReaxFF force field file imported from ADF software, and this time my simulation has been ended without warning. I compared the Ni atom parameters in two force field and I noticed that some of them are different.

yes, ReaxFF force fields are parameterized for specific purposes. you have to study the corresponding publications to figure out what exactly, so that you see, if the parameterization you are using is applicable for your specific use case (or not!).

Do you think that maybe some of force field files from ADF software could not be compatible with LAMMPS. I am asking this because both potential files work fine in ADF.

no. LAMMPS uses the same file format. however, as already indicated, your example input was not very meaningful for a classical MD code.

axel.