hi,
There are some questions on my project,
I build a DLC model (model-1) on diamon substrate by liquid quenching
method,
and the model consists of three group: group-DLC, group-sub, group-boundary.
All the atoms is carbon, and when i depostion the DLC, the potential between
all
atoms is tersoff.
I use the read_data commond read the data of model-1, to build the model-2.
I want compute the interfacial strength of the group-DLC and group-sub with
the commond 'compute group/group'. But in model-2, the DLC departs from
the sub. everything is same as the model-1, but the potential between the
DLC and sub is morse(cutoff is 4),
By now, I know the reason of the DLC depart from the sub is the potential
defference of the DLC and sub. In model-1, the potential of DLC and sub is
tersoff. In model-2, the potenial of DLC and sub is morse.
My question is whether there is commond to compute the interfacial strength
of different group? Only the commond 'compute group/group'?
Why did you post so many copies of this question to the lammps mailing list?
To answer your question, the compute group/group will not work for the
"tersoff" pair style.
And when I build the model-1, how could I define the potential between DLC
and sub?
It's not clear how to define interaction energies for
non-pairwise-additive potentials.
In your situation, I would try something like this:
1) Calculate the energy of only the "DLC".
2) Calculate the energy of only the "sub".
3) Calculate the energy the entire "DLC + sub" system
Subtract
E3 - (E1+E2)
You can use the "rerun" command to do this:
http://lammps.sandia.gov/doc/rerun.html
The "rerun" command can read a dump (trajectory) file( created during
a previous simulation) and recalculate the energy using new parameters
and atom settings.
You can use "rerun" to read the same trajectory file, and change the
atom types and tersoff parameters. You can do this to calculate the
energies of the "DLC" and "sub" groups in steps 1) and 2) above.
To calculate the energy of only the "DLC" system, for example, change
the atom type for all of the atoms in the "DLC" group. (to type 2, for
example).
set group DLC type 2
Then you would use a command like this to prevent these atoms from
being considered in your tersoff energy calculation:
pair_coeff * * SiC.tersoff C NULL
You can do the same thing when you calculate the energy of your "sub" system.
I think this works, but I have not tried it. If not, email back.
There is another way.
Cheers
Andrew