Cohesive energy for Graphite and Graphene using REBO potential

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1

Hello,

I am using the LAMMPS REBO potential to study graphite and graphene. Initially I am trying to compute the cohesive energy to make sure it is consistent with the values found in the literature (books/journal publications). When I compute the cohesive energy I am getting a value of -7.789eV, compared to a value of -7.4eV from the literature. Additionally, in Brenner's 2002 paper �A second-generation REBO potential energy expression for hydrocarbons�, it is stated in Table 1 that a value of -7.4eV (atomization energy) was used in the fitting scheme of the potential for graphite.

Looking through the mail-list archives I see that the REBO potential in LAMMPS is not exactly the REBO potential in the 2002 Brenner paper, but it has been stated for all intents and purposes they can be regarded as the same. So I assume it was also fit to the -7.4eV value and should reproduce this value as well.

I was wondering if anyone else has tried computing the cohesive energy for a graphite or graphene system using the LAMMPS REBO potential and what their value was. Or if it is possible the discrepancy I am seeing is due to the slight difference between the LAMMPS REBO and the 2002 Brenner REBO.

Also I should add that when I found the cohesive energy using the full Airebo (REBO, LJ, TORSION) potential I calculated a value of -7.4eV for the cohesive energy, which is consistent with the literature. I am using the 31Aug11 version of LAMMPS.

Thanks for your time

Regards,

-Justin

2

Maybe Steve Stuart wants to comment (CCd), but my
understanding is that the LAMMPS REBO potential
(which is just AIREBO with the LJ and torsion terms
turned off) is essentially exactly the 2nd generation
REBO. Thus I would not expect the large difference
in cohesive energy you are seeing. There have been
a few tweaks to AIREBO/REBO to fix bugs
that Steve's group has found. Can't remember when
the last one was, but you might re-try with the most
current LAMMPS version.

Steve

3

Steve,

Thank you for your reply. I tried finding the cohesive energy with the most recent version of LAMMPS available but I am still calculating a value of -7.79eV. So I guess none of the recent tweaks accounted for this issue.

-Justin