fix deform wiggle style!

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1

Dear Madam/Sir,

We have been trying to apply a cyclic bi axial load on a single crystal block of Al using EAM potential. At the beginning, we have tried to use wiggle style in fix deform in x-direction. The results show a linear increasing in the lx (size of the block in x direction), but we expected to have a sinusoidal behavior in the position applied load/displacement. We have tried also with Variable style but it seems that it is not compatible with npt when we try to apply the bi axial load on the model. So, I would be much obliged if you could explain why it has a linear behaviour by applying Sin load (wiggle style), and in the case of variable style what you suggest us to replace with npt.
Please find an example of the script in the attachment.
Thanks in advance and looking forward to hearing from you.

Regards,

Ramin Ghelichi

Oreint100.in (2.51 KB)

Al99.eam.alloy (762 KB)

2

Dear Madam/Sir,

We have been trying to apply a cyclic bi axial load on a single crystal block of Al using EAM potential. At the beginning, we have tried to use wiggle style in fix deform in x-direction. The results show a linear increasing in the lx (size of the block in x direction), but we expected to have a sinusoidal behavior in the position applied load/displacement. We have tried also with Variable style but it seems that it is not compatible with npt when we try to apply the bi axial load on the model. So, I would be much obliged if you could explain why it has a linear behaviour by applying Sin load (wiggle style), and in the case of variable style what you suggest us to replace with npt.
Please find an example of the script in the attachment.
Thanks in advance and looking forward to hearing from you.

Regards,

Ramin Ghelichi

Oreint100.in (2.51 KB)

Al99.eam.alloy (762 KB)

3

What is your evidence that the box size grows with time and
does not oscillate? You can use fix deform (any of its styles)
with fix npt, so long as you don't try to control the same
dimension with both.

Steve

4

I have checked the strain (and lx) in the load direction it grows linearly by time and no evidence of oscillation.

You are right about the npt I had put both load and npt on y direction.

Thanks

Ramin Ghelichi

5

Here is a simple 2d script, that uses fix deform wiggle and prints lx.
It oscillates and does not grow.

Steve

# 2d Lennard-Jones melt

units lj
dimension 2
atom_style atomic

lattice sq2 0.8442

region box block 0 20 0 10 -0.5 0.5

create_box 1 box
create_atoms 1 box
mass 1 1.0

velocity all create 1.44 87287 loop geom

pair_style lj/cut 2.5
pair_coeff 1 1 1.0 1.0 10.0

neighbor 0.3 bin
neigh_modify delay 0 every 1 check yes

fix 1 all nve
fix 2 all deform 1 x wiggle 5 2
fix 3 all enforce2d

dump 1 all atom 10 tmp.dump

thermo 100
thermo_style custom step temp pe lx

run 2000

6

Thanks Steve.
But what was the problem of our code. Using npt or not using fix enforced2d?
Anyway, thanks for your time and kind efforts.

Regards,
Ramin

7

I have no idea what your script's problem is. I don't think using
fix npt on other dimensions will have any effect on fix deform.

Steve