Hi,
I think you are neglecting the influence of temperature/ kinetic energy.
Please use "thermo_temp" instead of NULL for your compute stress/atom. This should give you the same results.
regards
Wolfgang
Hi Wolfgang,
I believe there is something wrong with the computation of stress/atom in association with the bop potential implementation in the LAMMPS. Because I tested it with other EAM potentials and it is working fine. But for bop, it is not working.
I tried with thermo_temp instead of NULL in the stress/atom command.
I tried with 300 K
I tried for a bigger model.
I tried with PPP and SSS boundaries.
In all cases, the pressure tensor (pxx, pyy, pzz, and so on) is not equal to the negative of global stress tensor calculated through -(the sum of stresses calculated from stress/atom) / volume.
I would like to know if anyone is facing the similar problem. Maybe I will try few more times and I will update.
Thanks,
Mathiazhagan S
To be honest I’m facing a much more rudimentary problem at the moment. I tried running your script but as I didn’t have your datafile I just used create_box etc. But as LAMMPS gets to the run command it complains about masses not being set… Which seems strange to me. Maybe one of the core developers can comment? And like Mathiazhagan said, for EAM everything runs fine.
Reading potential file CuH.bop.table with DATE: 2015-07-06
Reading potential file CuH.bop.table with DATE: 2015-07-06
ERROR: Not all per-type masses are set (src/velocity.cpp:64)
Last command: velocity all create $T 12345 mom yes rot no
The corresponding input script:
variable T equal 0.01
units metal
dimension 3
boundary p p p
atom_style atomic
#read_data data.al2cu_sample.lmp
lattice fcc 3.597
region box block 0 5 0 5 0 5
create_box 2 box
create_atoms 1 box
set group all type/fraction 2 0.05 12345
pair_style bop
pair_coeff * * AlCu.bop.table Cu Al
#set type 1 mass 26.982000
#set type 2 mass 63.546000
#pair_style eam/alloy
#pair_coeff * * AlCu.eam.alloy Cu Al
comm_modify vel yes cutoff 14.0
timestep 0.001
velocity all create $T 12345 mom yes rot no
compute peratom all stress/atom NULL
compute p all reduce sum c_peratom[1] c_peratom[2] c_peratom[3]
variable press equal -(c_p[1]+c_p[2]+c_p[3])/(3*vol)
thermo 10
thermo_style custom step temp etotal press v_press
fix 1 all nvt temp ${T} $T 0.01
run 100
To be honest I’m facing a much more rudimentary problem at the moment. I tried running your script but as I didn’t have your datafile I just used create_box etc. But as LAMMPS gets to the run command it complains about masses not being set… Which seems strange to me. Maybe one of the core developers can comment?
nothing unusual happening here. EAM potential files contain atom masses (which are applied when the potential is read), while most other potential files don’t (so you have to set the masses explicitly).
axel.