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Re: [lammps-users] Different slope in stress_strain curve
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Re: [lammps-users] Different slope in stress_strain curve


From: Asadollahzadeh <niliasadollahzadeh@...24...>
Date: Fri, 7 Jul 2017 16:40:17 +0430

Hi Dr.Axel...
Please guidance me ... I'm confused!!!

sincerely
Nili


On Fri, Jul 7, 2017 at 10:17 AM, Asadollahzadeh <niliasadollahzadeh@...24...> wrote:
Hi my friends!
I am using LAMMPS to simulate an  eam  system recently. I have met a problem. 
When I used boundary as "p s p" has different slope with boundary as         "s s s".
I think, these should be different on "pick" no on "slope"
I had use the commands:


units           metal
atom_style      atomic
boundary        p s p                       # another runs with boundary as "s s s"


region          simbox block -300 300 -300 300 -300 300   units box
create_box      2 simbox

lattice         fcc 4.0500
region          cube block -30 30 -30 30 -30 30 units box
create_atoms 1 region cube
set             group all type/fraction 2 1 12393 
mass 1 63.546
mass 2 26.9815

pair_style eam/alloy
pair_coeff * * AlCu.eam.alloy Cu Al

min_style         cg
minimize          1.0e-8 1.0e-8 1000 10000

velocity          all create 100 123456 mom yes rot yes

fix              0  all nvt temp 100 100 0.1
fix              1  all nve 

##############################################################################

reset_timestep    0

compute  ymin   all  reduce  min  y 
compute  ymax   all  reduce  max  y 

compute  xmin   all  reduce  min  x 
compute  xmax   all  reduce  max  x

compute  zmin   all  reduce  min  z 
compute  zmax   all  reduce  max  z



variable  length_y   equal  c_ymax-c_ymin
variable  length_x   equal  c_xmax-c_xmin
variable  length_z   equal  c_zmax-c_zmin

variable    fix     equal  5
variable    lim01   equal  c_ymin
variable    lim02   equal  c_ymin+v_fix
variable    lim03   equal  c_ymax-v_fix
variable    lim04   equal  c_ymax


thermo_style  custom  step c_ymin  c_ymax  c_xmin  c_xmax  c_zmin  c_zmax
thermo      100000

log           log1.txt
run 0


region          lower block  INF  INF  ${lim01}  ${lim02}  INF  INF  units  box

region          upper block  INF  INF  ${lim03}  ${lim04}  INF  INF  units  box   
 
variable        midlength  equal  ${length_y}-2*${fix} 

group           lower region lower
group           upper region upper

velocity        lower set  0  0      0   units box
velocity        upper set  0  0.06 0   units box

fix             3 lower setforce 0 0 0
fix             4 upper setforce 0 0 0


group           middle subtract all upper lower  



compute    mystress middle stress/atom NULL virial

compute    reducedstress middle reduce sum c_mystress[2]     # press*volume

variable    middleVolume equal (${length_x}*${midlength}*${length_z})      
variable    stress equal (c_reducedstress)/(10^4*${middleVolume})
variable        strain equal (0.5*(1-(1/((step*0.001*0.06/(${midlength}))+1)^2)))          #Almansi strain

fix        5    middle  nvt temp 100 100 0.1 
fix        6    lower   nve
fix        7    upper   nve

thermo          1000
thermo_style    custom step v_strain v_stress

dump            2  all custom 1000     dumpnormal.lammpstrj    

log             logFigure.txt
run             200000


May anyone give some advice to me ?

Thank you in advance.

regards,
Nili