Weird NEB results
Posted: Tue Jun 21, 2011 3:05 pm
Hello all
I have been doing some simple NEB calculations for diffusion of H from an FCC to a HCP binding site on a Os(0001) closed packed surface. The INCAR I am using is as follows:
# Regular
SYSTEM = Os_NEB
ISYM = 0
NSW = 2000
EDIFF = 0.1E-6
EDIFFG = -0.01
ENCUT = 354
GGA = RP
LWAVE = .TRUE.
LCHARG = .FALSE.
PREC = medium
ISIF = 0
# ISPIN = 2
# Speedup
NPAR = 2
NSIM = 4
IALGO = 48
LPLANE = .TRUE.
LREAL = Auto
#NEB
ICHAIN = 0
IMAGES = 8
SPRING = -5.0
LCLIMB = .FALSE.
LTANGENTOLD = .FALSE.
LDNEB = .FALSE.
# Optimizer2
IBRION = 3
POTIM = 0.00
IOPT = 2
MAXMOVE = 0.10
FDSTEP = 5E-3
And the neb.dat file after using nebresults.pl script gives:
0 0.000000 0.000000 -0.001496 0
1 0.181737 0.017571 -0.002813 1
2 0.368447 0.037901 0.001344 2
3 0.551387 0.046485 0.000317 3
4 0.729682 0.049821 0.000008 4
5 0.906971 0.052864 -0.000198 5
6 1.086388 0.055378 -0.001679 6
7 1.272234 0.051754 -0.002708 7
8 1.463062 0.033695 0.008068 8
9 1.643894 0.018108 0.000795 9
What is bugging me is the look of the minimum energy path figure. As you can see from the neb.dat the force projection on to tangent for each image is very small but I thought that unless it is a minima or maxima it should be a little bit larger and I thought that for a smooth curve an increase in energy would have positive force and decrease would have a negative force but here it is just random with negative forces both before and after the transition state etc.
At least would anyone please look at my mep.eps figure and hopefully give me some advice of what might be wrong.
I have done similar calculations for other metals in Dacapo and there I always got a smooth curve, not with these tiny bumps all over the ME path.
Thanks,
sig
p.s. I attached the mep.eps image as well as the movie.xyz generated using nebresults.pl
I have been doing some simple NEB calculations for diffusion of H from an FCC to a HCP binding site on a Os(0001) closed packed surface. The INCAR I am using is as follows:
# Regular
SYSTEM = Os_NEB
ISYM = 0
NSW = 2000
EDIFF = 0.1E-6
EDIFFG = -0.01
ENCUT = 354
GGA = RP
LWAVE = .TRUE.
LCHARG = .FALSE.
PREC = medium
ISIF = 0
# ISPIN = 2
# Speedup
NPAR = 2
NSIM = 4
IALGO = 48
LPLANE = .TRUE.
LREAL = Auto
#NEB
ICHAIN = 0
IMAGES = 8
SPRING = -5.0
LCLIMB = .FALSE.
LTANGENTOLD = .FALSE.
LDNEB = .FALSE.
# Optimizer2
IBRION = 3
POTIM = 0.00
IOPT = 2
MAXMOVE = 0.10
FDSTEP = 5E-3
And the neb.dat file after using nebresults.pl script gives:
0 0.000000 0.000000 -0.001496 0
1 0.181737 0.017571 -0.002813 1
2 0.368447 0.037901 0.001344 2
3 0.551387 0.046485 0.000317 3
4 0.729682 0.049821 0.000008 4
5 0.906971 0.052864 -0.000198 5
6 1.086388 0.055378 -0.001679 6
7 1.272234 0.051754 -0.002708 7
8 1.463062 0.033695 0.008068 8
9 1.643894 0.018108 0.000795 9
What is bugging me is the look of the minimum energy path figure. As you can see from the neb.dat the force projection on to tangent for each image is very small but I thought that unless it is a minima or maxima it should be a little bit larger and I thought that for a smooth curve an increase in energy would have positive force and decrease would have a negative force but here it is just random with negative forces both before and after the transition state etc.
At least would anyone please look at my mep.eps figure and hopefully give me some advice of what might be wrong.
I have done similar calculations for other metals in Dacapo and there I always got a smooth curve, not with these tiny bumps all over the ME path.
Thanks,
sig
p.s. I attached the mep.eps image as well as the movie.xyz generated using nebresults.pl