Tersoff Potential for LJ units

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1

Dear all,

The Tersoff 1994 potential files are parameterized for metal units.

How can I get the parameters of it for LJ units?

Best Wishes!

2

Create a new Tersoff potential file and manually convert everything in the original potential file to LJ units.

Ray

3

what are the reference values?

4

What do you mean by reference values?

Open up a Tersoff potential file, such as $YOUR_LAMMPS/potentials/Si.Tersoff and have a look.

5

Thanks.

I saw the parameters. But the question is how can I convert it to LJ.

If I convert the metal units value into LJ. I should have reference values. Right?

for example, if a =10 nm, b= 30 nm. In LJ, a = 1 , b =3 .

6

You can pick whatever you like. That is what reduced units are about.

It is going to be far from trivial though.

7

thanks!

I think this is not that simple, right?

If I convert everything to LJ, the dynamics maybe change.

What do you think?

Also ,some parameters in the file are unitless. How to deal with this? same technique?

Best Wishes!

8

thanks!

I think this is not that simple, right?

If I convert everything to LJ, the dynamics maybe change.

What do you think?

Not if you do it correctly.

Also ,some parameters in the file are unitless. How to deal with this? same technique?

I can’t say, they probably should be unchanged.

9

I’ve said this before. If you input
the correct params, then you can do
an identical simulation in any units. For LJ vs

anything (metal, real, etc) you will need
to pick the density and energy scales correctly.

I suggest you start with a simple pair lj/cut potential
and 1 snapshot of atoms and get perfect
agreement, then work your way up to tersoff

from there.

Steve