Reason of energy fluctuation ?!

Message

Leny · #1 Post by **Leny** » Thu May 03, 2012 1:53 pm

Hello Vasp users,
Does any one know what the reason of energy fluctuation, I am calculating adsorption energy of H on Pt surface but I don?t get energy convergence it is as it is shown here :

steps Force Energy difference
0 0.104192 -516.933783 0
1 0.087083 -516.93512 -0.001337
2 0.064635 -516.937975 -0.004192
3 0.060439 -516.938692 -0.004909
4 0.071429 -502.27827 14.6555
5 0.066329 177.659246 694.593
6 0.070372 10705.48892 11222.4
7 0.058427 -516.927188 0.006595
8 0.035486 -516.949669 -0.015886
9 0.025549 -516.950132 -0.016349
10 0.024623 -516.950446 -0.016663
11 0.022644 10312.13344 10829.1
12 0.020135 506.906548 1023.84
13 0.016058 -516.952963 -0.01918
14 0.020905 27731.48427 28248.4
15 0.016182 -507.885289 9.04849
16 0.016608 -516.951145 -0.017362
17 0.010207 -516.953052 -0.019269
18 0.011404 9195.241865 9712.18
19 0.007289 2624.268755 3141.2

and here is the INCAR:

# Regular
SYSTEM = Pt_1H
ISYM = 0
NSW = 200
EDIFF = 0.1E-6
EDIFFG = -0.01
ENCUT = 450
GGA = RP
LWAVE = .FALSE.
LCHARG = .FALSE.
PREC = medium
ISIF = 0
IDIPOL = 3
# ISPIN = 2

# Speedup
NPAR = 2
NSIM = 4
IALGO = 48
LPLANE = .TRUE.
LREAL = Auto

# Optiizers
IBRION = 3
POTIM = 0.0
IOPT = 2
MAXMOVE = 0.15

I really appreciate any help with this problem, any idea for what it could be because I am new too I have not a big experience with this field.

best regards,

alex · #2 Post by **alex** » Thu May 03, 2012 3:19 pm

Your system was probably not converged in many steps. The wavefunction is shitty though.
POTIM = 0

Leave out IDIPOL

In short, start with as few extra switches as possible.

Cheers,

alex