Hello everyone!
I am running H2 dissociative adsorption calculations on graphene. One of the things I do is study the dissociative adsorption behavior in the presence of electric fields. However, the results that I am getting are not what I expect. The change in the dissociation barrier and the chemisorption energy when an electric field is applied, relative to the case without an electric field, is tiny, even for electric fields as high as 1 eV/A. This is surprising as previous papers (they used DMOL3 code) have shown that around this value the process becomes barrierless, but this is not seen in my calculations. I have attached my INCAR here, in case there is some sort of mistake in it or in the way that I am applying the electric field. The INCAR is the only input file I change when applying the electric field (POTCAR and KPOINTS remain the same, the CONTCAR from the optimized no-electric-field case becomes the new POSCAR). The calculation finishes, and there is electronic and ionic convergence.
I also wonder if an additional correction (during the post-processing) is required. I noticed that another user faced the same issue as I a while back (different gas and different 2D material, but the same issue with the adsorption energies), but there was no update in their case. I also found a blog post where a VASP user talked about applying a dipole energy correction after the calculations, but examining this in greater detail revealed that this is already included in the dipole correction that we apply. So, considering it again would be redundant. With these issues that other users have faced, I am wondering if any other corrections to the energy values are required during post-processing?
INCAR:
Code: Select all
SYSTEM = GRAPHENE
!!SYSTEM INITIALIZATION!!
ISTART = 0
ICHARG = 2
!!ELECTRONIC STEPS!!
ALGO = Normal
!!GGA = PE
ENCUT = 500
ISMEAR = 0
SIGMA = 0.05
EDIFF = 1E-6
NSW = 1000
!!IONIC STEPS!!
PREC = Accurate
IBRION = 2
!!NFREE = 2
POTIM = 0.15
EDIFFG = -0.01
NELM = 500
NELMIN = 5
!!SMASS = 1.0
!!CELL RELATED!!
ISIF = 2
ISYM = 0
LREAL = Auto
SYMPREC = 1E-4
!!CORRECTIONS!!
IVDW = 11
IDIPOL = 3
LDIPOL = .TRUE.
DIPOL = 0.5 0.5 0.5
!!MAGNETIZATION!!
ISPIN = 2
!!NUPDOWN = 0
MAGMOM = 162*0.7 0.7 -0.7
!!NELECT = 448
EFIELD = 1.0
!!GENERAL/CALCULATION OPTIMIZATION!!
LWAVE = .FALSE.
LCHARG = .FALSE.
NCORE = 4
!!NPAR = 4
!!NEB CALCULATION!!
!!NWRITE = 2
!!IMAGES = 16
!!SPRING = -3
!!ICHAIN = 0
!!LCLIMB = TRUE
!!IOPT = 3
!!MAXMOVE = 0.2
!!TIMESTEP = 0.1