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Re: [lammps-users] strain effect on primary radiation damage
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Re: [lammps-users] strain effect on primary radiation damage


From: Julien Guénolé <julien.guenole@...4839...>
Date: Fri, 8 Sep 2017 12:27:26 +0200

On 08/09/17 12:01, kia krn wrote:
Dear LAMMPS users
i want to see strain (uniaxial and hydrostatic) effect on primary radiation damage. i used fix deform command as follows:

# Store final cell length for strain calculations

variable tmp equal "lz"

variable L0 equal ${tmp}

print "Initial Length, L0: ${L0}"



# DEFORMATION

reset_timestep 0

fix relax all nvt temp 300 300 1 


variable srate equal 1.0e10

variable srate1 equal "v_srate / 1.0e12"

fix 2 all deform 1 z erate ${srate1} units box remap x
you are applying a strain rate, not a constant strain. That is expected to have the strain in you system increased during a run.

To my opinion, you have two solutions:
1 - apply the strain once, with the command change_box (do not forget to remap atoms coordinates), and then perform you dynamics.
2 - apply the strain with a strain rate, with the command fix deform followed by a dynamics (strain rate and dynamic duration should give you the desired strain). Then, after reaching the desired strain, perform a dynamics without the fix.




variable strain equal "(lz - v_L0)/v_L0"

variable p1 equal "v_strain"


fix def1 all print 100 "timestep  ${p1} " file Al_100.def1.txt screen no

dump     strain all custom 100 dump.pos_strain.*.dat id type x y z vx vy vz

# Display thermo

thermo  100
thermo_style custom step v_strain temp vol ke pe press 

run              1000

#Starting PKA run

reset_timestep 0
unfix      relax
unfix    2
unfix     def1
undump    strain

# Make boundary atoms fixed
velocity boundary set 0.0 0.0 0.0
.....
...
....
but in output i got that strain continuous to increase. 
output looks as follows:

run              1000
Memory usage per processor = 121.087 Mbytes
Step v_strain Temp Volume KinEng PotEng Press 
       0 -2.3037689e-015    296.29855    1877733.1    4136.3178    -381917.8    320.92044 
     100        0.005     293.1684    1887121.8     4092.621   -381836.58   -3112.3114 
     200         0.01    291.87574    1896510.5    4074.5755   -381743.03   -6493.0218 
     300        0.015    288.95104    1905899.1    4033.7468   -381595.33   -9572.9171 
     400         0.02    287.88627    1915287.8    4018.8826   -381442.41   -12567.967 
     500        0.025    284.90018    1924676.5     3977.197   -381235.09   -15257.786 
     600         0.03    282.77329    1934065.1    3947.5056   -381014.32   -17819.607 
     700        0.035    282.10727    1943453.8     3938.208   -380790.67   -20348.147 
     800         0.04    280.77037    1952842.5    3919.5449   -380536.32   -22630.945 
     900        0.045    278.92129    1962231.1    3893.7319   -380255.03   -24719.269 
    1000         0.05     278.2035    1971619.8    3883.7115   -379971.37   -26736.306

but i want to apply for example 1% tensile strain and then equilibrate/ relax system at this strain. so your kind suggestion/solution how should i do this?

Thanx in advance
Kiakrn

-- 
*************************************************
Dr. Julien GUÉNOLÉ
Postdoctoral researcher
-----------------------
Department of Materials Science & Engineering
Institute 1: General Material Properties
Friedrich-Alexander-University Erlangen-Nürnberg
Martensstr. 5, 91058 Erlangen, Germany
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Phone [office] (+49) 91 31 85 27 486
Email          julien.guenole@...4839...
Web            http://www.julien-guenole.fr
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