Problem with fix_move command

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1

Hi all,

I am trying to do static simulation of edge dislocation motion in LAMMPS.

After initial minimization using cg method, i am trying to apply shear in the upper region ( keeping the lower region fixed) as-

units		metal
boundary	p p p

atom_style	atomic


read_data    data10.dislocation


pair_style      eam


pair_coeff      Al_jnp.eam


region       lower block INF INF INF -7.417767e+001 INF INF units box

region       upper block INF INF  7.183940e+001  INF INF INF units box 
region       left block  INF 10 INF INF INF INF INF units box
region       right block 1.017064e+002 INF INF INF INF INF  units box  

group        boundary union lower upper left right

group        mobile subtract all boundary

compute         csp all centro/atom fcc

dump            2 all cfg 1000 edge.* id type xs ys zs c_csp
 
thermo          100
thermo_style    custom step  temp pe etotal press vol atoms lx ly lz

min_style      cg

fix           1 all box/relax   iso 0.0
fix            2 boundary setforce NULL  0.0  NULL

minimize        1e-6 1e-6 10000 10000


unfix          1


unfix          2


##################################COMPUTE STRESSES#####################################


compute          stress mobile stress/atom


compute           shearstress mobile reduce sum c_stress[4]


variable          shear  equal (-c_shearstress/(lx*lz*166.01701))##### Stress in ev/Angstroms units


variable           shearstress equal (v_shear*160.2)######## Stress in GPa


################################################APPLY SHEAR################################################


label             shearmove


variable          a loop 100


variable           n equal $a


variable             dx equal .0016601701 ###############initial shear strain==1e-5


variable           strain equal (v_dx*v_n)

thermo          50
thermo_style    custom step  temp pe etotal press lx ly lz v_stress v_strain



fix                  2 lower setforce 0.0 0.0 0.0


fix                  3 upper move v_dx NULL NULL NULL NULL NULL#### Applies shear


run                  10


unfix               2


min_style                  cg


fix                        1 all box/relax iso 0.0


fix                        2 boundary setforce NULL 0.0 NULL


minimize                   1e-9 1e-9 100000 100000###### minimization


next                          a


jump            in.shear     shearmove


But it seems that the shear force is not transmitted in the whole;


only upper region atoms are moving.... Also, the temperature is increasing...


Why this all is happening..?? Please help..!!!!???


Thanks to all..


sagar
2

Hi all,

I am trying to do static simulation of edge dislocation motion in LAMMPS.
After initial minimization using cg method, i am trying to apply shear in
the upper region ( keeping the lower region fixed) as-

[...]

But it seems that the shear force is not transmitted in the whole;

why should it? during the MD parts,
you are only moving a part of the system but not time integrating the rest.

only upper region atoms are moving.... Also, the temperature is
increasing...

temperature is meaningless in minimizations and has no impact on fix move.

Why this all is happening..??

because you tell LAMMPS to do this and it does.

Please help..!!!!???

talk to your adviser. that is what advisers are for. mailing lists are
no substitute for that.

axel.