compression test

Hello

I am a new user of LAMMPS and I want to do a compression test.

I did a compression model but the results seems weird. The stress always increase during the compression test. It never decreases and I know it’s wrong.

I send my model, can you say what are my errors?

Thank you and have a nice day!

Mai Thi

units metal

dimension 3

boundary p p p

atom_style atomic

neighbor 0.3 bin

neigh_modify delay 5

#create geometry

lattice bcc 3.304

region box block 0 1 0 1 0 1

create_box 1 box

create_atoms 1 box

#Interatomic potentials

pair_style eam/alloy

pair_coeff * * Ta.txt Ta

#equilibrate

velocity all create 300.0 100 rot yes dist gaussian

fix 1 all npt temp 300.0 300.0 100.0 iso 0.0 0.0 1000.0

fix 2 all temp/rescale 1 300.0 300.0 0.001 1.0

thermo 200

thermo_style custom step lx ly lz pxx pyy pzz temp

timestep 0.005

run 2000

unfix 1

unfix 2

variable l equal lx

variable l0 equal $l

#compression

reset_timestep 0

fix 1 all nvt temp 300.0 300.0 100.0

fix 2 all temp/rescale 1 300.0 300.0 0.001 1.0

fix 3 all deform 1 x erate 0.005 units box remap x

variable strain equal “(lx-v_l0)/v_l0”

#For units metal pressure is 1 (bars) = 1/10000(GPa)

variable p1 equal “-pzz/10000”

#For units metal distance is 1 (Angstrom) = 0.0000001 (cm)

variable l1 equal lx*0.0000001

fix results all print 500 “{p1} {strain}” file results.txt screen no title “stress strain”

thermo 200

thermo_style custom step v_strain temp v_l1 v_p1 press

#dump 1 all xyz 100 dump.file.xyz

dump 2 all image 100 image.*.jpg type type zoom 1.6 adiam 1.5

#dump_modify 2 backcolor white

#dump_modify 2 boxcolor black

run 40000

Hello

I am a new user of LAMMPS and I want to do a compression test.

I did a compression model but the results seems weird. The stress always increase during the compression test. It never decreases and I know it’s wrong.

For starters, please examine the lammps log file carefully and correct the enormous mistakes lammps is warning you about.

Axel