about simulating unaxial tension

Hi all,

I want to simulation unaxial tension. In my model, I use periodic boundary for all three directions.
boundary p p p

and, I use fix deform for adding strain increment, and fix npt to control the pressure of other 2 directions.

fix 5 all deform 100 x erate 0.01 units box

fix 6 all npt temp 300 300 0.005 y 0 0 0.05 z 0 0 0.05

My question is:

  1. Is it OK for simulating unaxial tension?

  2. In another article, they use the same boundary condition, but they use NVT with fix deform for tension.

  3. Can you give me some advice for simulating poisson’s ratio?

Best regards,

MC

Comments below.

Steve

Hi all,

I want to simulation unaxial tension. In my model, I use periodic boundary
for all three directions.
boundary p p p

and, I use fix deform for adding strain increment, and fix npt to control
the pressure of other 2 directions.

fix 5 all deform 100 x erate 0.01 units box

fix 6 all npt temp 300 300 0.005 y 0 0 0.05 z 0 0 0.05

My question is:

1. Is it OK for simulating unaxial tension?

That's up to you. The doc page explains precisely what
this does - you have to decide if that's what you want.

2. In another article, they use the same boundary condition, but they use
NVT with fix deform for tension.

From my viewpooint, the volume cannot change using NVT, so the possion's
ratio should be 0.5. But it is controversial to the real state (in my
simulation, the poisson's ratio of material is about 0.2). Is it wrong to
use NVT?

Again, up to you. NVT is just a thermostat. It doesn't conflict with
fix deform, though for large deformation rates, you may want to
be careful about what you define as the thermal component of
velocity (= temperature).

3. Can you give me some advice for simulating poisson's ratio?

I don't know what this means.