compute stress

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1

Hi all,
I have a question about computing the stress. I wrote in my code to compute the pressure of entire system, and also I wrote "dump’ to have an output for stress, but the problem is that lammps does not give me any output file for stress. I s there any problem in my code. I appreciate if you could help me to find an approach for this problem.

Thanks,
Elham

#set dimension and boundry condition
dimension 3
boundary p p p

#set units type,atom type and neigborhood
units metal
atom_style atomic
##neigh_modify every 1

#create big box
lattice fcc 3.52
region big sphere 0.0 0.0 0.0 20.0 units lattice
create_box 1 big

#create main atoms
region eli sphere 0.0 0.0 0.0 25.0 side in
create_atoms 1 region eli

group e1 region eli

#create second atoms
region hap sphere 55.5 0.0 0.0 30.0 side in
create_atoms 1 region hap

group e2 region hap

#create third atoms
region cap sphere 0.0 65.0 0.0 35.0 side in
create_atoms 1 region cap

group e3 region cap

#create forth atoms
region mos sphere 75.5 65.0 0.0 40.0 side in
create_atoms 1 region mos
group e4 region mos

#add all the nanoparticles

group all union e1 e2 e3 e4

#set the mass of atoms
mass 1 58.69

#set the velocity of atoms
velocity all create 600.0 4928459 rot yes mom yes

#define the eam
pair_style eam
pair_coeff * * Ni_u3.eam
##pair_coeff 1 1 0.7 2.517 ##For LJ

#Specify build neighborlist, use cutoff+0.3 A
neighbor 2 bin

#Frequency to rebuild neighborlist
neigh_modify every 1 delay 0 check yes

fix pip all nvt temp 600 600 0.0050

minimize 1.0e-6 1.0e-8 1000 1000

#set timestep
timestep 0.0005 #0.5 femtosecond

compute Fall all pressure NULL pair bond

#specify values to show in run
thermo 1000
thermo_style custom step temp pe ke etotal

dump Nidump all atom 1000 sphere-temp-600-4diff-nps.dump

dump Ni all local c_nan 1000 4diff-nps-sphere-temp600.stress

###dump 1 all custom 1 sphere11_temp1000.txt id type x y z
#specify the method of calculation

run 100000

2

Hi all,
         I have a question about computing the stress. I wrote in my code to
compute the pressure of entire system, and also I wrote "dump' to have an
output for stress, but the problem is that lammps does not give me any
output file for stress. I s there any problem in my code. I appreciate if
you could help me to find an approach for this problem.

run your input with -echo screen and observe carefully. LAMMPS will
*tell* you what is wrong and you'll see the line which causes the
issue. i've already pointed that one out in a previous e-mail.

axel.

3

The problem is in my second Dump “**dump Ni all local c_nan 1000 4diff-nps-sphere-temp600.**stress” It should be c_Fall, not c_nan, but again it shows me an error that " expected integer parameter in input script or data file" . I cannot figure it out why it shows me this error. this error is not in lammps manual.

4 
Elham, 

Please check the "dump" command more carefully. It expects an integer which is a number not a compute one ! and also do you want to dump pressure of the system or stress per atom!

dump ID group-ID style **N** file args

Thanks,


Sara