[lammps-users] Question about "fix indent" command

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1

Dear All,

I have 2 questions about this command,

First, can I apply two indenters simultaneously to some material, for example, one is below and the other is at top of the material;

Second, how to set the value of the force constant k. In the example, 1000.0 is used, but I
don’t know the reason and the rule to set this constant.

Many thanks.

2

I have 2 questions about this command,
First, can I apply two indenters simultaneously to some material, for
example, one is below and the other is at top of the material;

yes

Second, how to set the value of the force constant k. In the example, 1000.0
is used, but I
don't know the reason and the rule to set this constant.

It basically sets the stiffness of the interaction between the
indenter and atoms, as in the eq in the doc page. So you need
to decide what kind of indenter (hard, soft) makes sense for
your model.

Steve

3

Thanks Steve,

I would like to make sure the meaning of “vel” in the fix indent command.

What is the meaning when it is positive or negative in some direction?

In addition, if I want to use hard indenter, how I should set the spring constant?

You used 5.3uN/A^2 in your paper to study Au surface, why did you used this value?

Thanks

4

A pos/neg vel means the indenter will move in one direction
vs the other in the simulation box. I think the indenter
value is just a guestimate. If the indenter is replacing
atoms, then you want it to exclude atoms with about the
same stiffness as real atoms would exclude others. If you
play with different values, you should find something good. Too
large and you won't be able to take a reasonable timestep.

Steve