I would like to reproduce the data of adsorption energies published in paper.
For example, they say the adsorption energy for Li atom on graphene is -1.19 eV (estimated by GGA-PBE). I used vasp (5.4) code using parameters indicated in the paper and estimated total energy for
Supercell 4x4x1 of graphene:
Graphene with one Li atom on its surface:
One Li atom (estimated from bcc structures):
Therefore, the adsorption energy should be
-296.35605 eV -[(-295.29545 eV) + (-1.909 eV)] = +0.848 eV. It is inconsistent with the previous calculation.
If I use total energy for the isolated Li atom of
-0.29471258 eV, the obtained adsorption energy is
-0.767 eV. Both have a big gap with the published data. I wonder if there is a trick to accurately estimate the adsorption energy?