Thanks for your replies.
The error is "It is needed to set attributes like q " when I used "Fixed
efield" commands which endorses your opinion about AIREBO potential, and
it obviously says it is charge-based potential.
For your inforamtion, I was told, my professor, to do the simulation with
this force field, and somehow I am limited to use this. Otherwise, I have
strong reasons to prove that it is not the right FF in my case.
In that case, you should argue/reason with your advisor by exploring other
possibilities, e.g. ReaxFF or COMB. You are not going to get a response to
the external field with AIREBO anyway.
I am not quite sure, but according to some articles which I read about
electronic properties of graphene maybe I should use DFT (Density Function
Theory) approach in order to determine the electron structure of the
lattice and then define an interaction between those and charged particles.
? Now, my question is that how I can implement DFT in lammps?
Using DFT is beyond the scope of this mailing list. You can not use DFT in
LAMMPS, which is a classical MD code.
Ray
Thanks for your replies.
The error is "It is needed to set attributes like q " when I used "Fixed
efield" commands which endorses your opinion about AIREBO potential, and it
obviously says it is charge-based potential.
For your inforamtion, I was told, my professor, to do the simulation with
this force field, and somehow I am limited to use this. Otherwise, I have
strong reasons to prove that it is not the right FF in my case.
In that case, you should argue/reason with your advisor by exploring other
possibilities, e.g. ReaxFF or COMB. You are not going to get a response to
the external field with AIREBO anyway.
I am not quite sure, but according to some articles which I read about
electronic properties of graphene maybe I should use DFT (Density Function
Theory) approach in order to determine the electron structure of the lattice
and then define an interaction between those and charged particles. ? Now,
my question is that how I can implement DFT in lammps?
Using DFT is beyond the scope of this mailing list. You can not use DFT in
LAMMPS, which is a classical MD code.
Ray
Of course, I know other codes like GAUSSIAN do this.
Actually, it looks like Axel just recently added some preliminary
support for DFT in LAMMPS, (but I don't think it works with an
external field yet):
http://lammps.sandia.gov/doc/fix_qmmm.html
According to the documentation, it currently links to the
quantum-espresso code (which uses plane-waves instead of
atomic-orbital basis).
http://www.quantum-espresso.org/users-manual/
It was written in a way to allow it to link with other DFT
implementations. (Axel is asking for help doing this.) This seems
like an exciting feature. I don't use DFT, so I hesitate to say more.
Cheers
Andrew
[...]
Using DFT is beyond the scope of this mailing list. You can not use DFT in
LAMMPS, which is a classical MD code.
Ray
Of course, I know other codes like GAUSSIAN do this.
Actually, it looks like Axel just recently added some preliminary
support for DFT in LAMMPS, (but I don't think it works with an
external field yet):
http://lammps.sandia.gov/doc/fix_qmmm.html
According to the documentation, it currently links to the
quantum-espresso code (which uses plane-waves instead of
atomic-orbital basis).
http://www.quantum-espresso.org/users-manual/
It was written in a way to allow it to link with other DFT
implementations. (Axel is asking for help doing this.) This seems
like an exciting feature. I don't use DFT, so I hesitate to say more.
yes. DFT is the way to go. ReaxFF will only get you halfway. it won't
compute the impact of the electric field on the electron distribution,
but that is crucial, as that will impact the charge distribution which
in turn will impact the force on the atoms. however, doing this
correctly is far from trivial. it can be quite difficult to converge
such wavefunction, especially for a system that is highly polarizable.
there is no need to use the QM/MM interface that andrew is referring
to. you need the real deal. also the QM/MM interface currently does
mechanical coupling a la ONIOM only. so that will neglect
electrostatic interactions beyond the classical parameterization
anyway.
axel.