NEB calculation with strage Relative energy
Posted: Sat Oct 23, 2021 5:17 am
VTST Community,
In my first NEB calculation I observed very strange relative energy. The procedure I followed as mentioned in the VTST tools. I have optimized the IS and FS with standard VASP (the energy is almost same with VTST). In NEB calculation forces were converged for all the images, however, I got the data (nebefs.pl) as below:
Image Force Stress Volume Magnet Rel Energy
0 0.00000000 6.11124600 3526.99 0.00000000 0.00000000
1 0.00500100 9.78947900 3526.99 0.00000000 -138.22840000
2 0.01282100 8.71075500 3526.99 0.00000000 -138.07530000
3 0.02115400 8.56068000 3526.99 0.00000000 -136.92880000
4 0.01310700 8.31480200 3526.99 0.00000000 -137.26860000
5 0.02082400 8.92213100 3526.99 0.00000000 -137.34470000
6 0.00000000 0.00000000 3526.99 0.00000000 0.43010000
But the interesting observation is when I did Single Point calculation of that images I got different Relative energies, as follows:
0 0.0
1 1.2331
2 1.38191
3 2.18835
4 1.69337
5 1.67068
6 0.430029
My INCAR parameters are:
IVDW = 12 (DFT-D3 method of method with no damping)
LDAU = .TRUE. (Activate DFT+U)
LDATYPE= 2 (Dudarev; only U-J matters)
LDAUL = -1 -1 -1 2 (Orbitals for each species)
LDAUU = 0 0 0 0 5 (U for each species)
LDAUJ = 0 0 0 0 0 (J for each species)
LMAXMIX= 4 (Mixing cut-off; 4-d, 6-f)
# Global Parameters
ISTART = 1 (Read existing wavefunction; if there)
ISPIN = 1 (Non-Spin polarised DFT)
ALGO = VF
LREAL = AUTO (Projection operators: automatic)
ENCUT = 400 (Cut-off energy for plane wave basis set, in eV)
PREC = Normal (Precision level)
LWAVE = .FALSE. (Write WAVECAR or not)
LCHARG = .FALSE. (Write CHGCAR or not)
ADDGRID= .TRUE. (Increase grid; helps GGA convergence)
ISYM = 0
LASPH = T !use for LDA+U, hybrid or meta-GGA in f- and 3d-elements
# Budged Elastic Band (NEB)
LCLIMB = .TRUE.
LTANGENT = .TRUE. (following Graeme Suggestion with lower setup)
IMAGES = 5 (#of images without 2 endpoints,#of nodes=#of images/divisible,nodesOfGgroup/image)
NSW = 500 (number of ionic steps)
ISMEAR = 0 (gaussian smearing method)
SIGMA = 0.05 (please check the width of the smearing)
IBRION = 3 (do MD with a zero time step)
POTIM = 0 (Zero time step so that VASP does not move the ions)
SPRING = -5.0 (spring force (eV/A2) between images)
LCLIMB = .TRUE. (turn on the climbing image algorithm)
ICHAIN = 0 (Indicates which method to run. NEB (ICHAIN=0) is the default)
IOPT = 1 (LBFGS = Limited-memory Broyden-Fletcher-Goldfarb-Shanno)
# Relaxation
NELM = 200 (Max electronic SCF steps)
NELMIN = 6 (Min electronic SCF steps)
EDIFF = 1E-07 (SCF energy convergence; in eV)
ISIF = 2 (Stress/relaxation: 2-Ions, 3-Shape/Ions/V, 4-Shape/Ions)
EDIFFG = -0.025
# Surface dipole corrections
IDIPOL=3 ! 3 is for surfaces
LDIPOL= T
Would you please help me to find source of strange relative energies?
Thanks!
In my first NEB calculation I observed very strange relative energy. The procedure I followed as mentioned in the VTST tools. I have optimized the IS and FS with standard VASP (the energy is almost same with VTST). In NEB calculation forces were converged for all the images, however, I got the data (nebefs.pl) as below:
Image Force Stress Volume Magnet Rel Energy
0 0.00000000 6.11124600 3526.99 0.00000000 0.00000000
1 0.00500100 9.78947900 3526.99 0.00000000 -138.22840000
2 0.01282100 8.71075500 3526.99 0.00000000 -138.07530000
3 0.02115400 8.56068000 3526.99 0.00000000 -136.92880000
4 0.01310700 8.31480200 3526.99 0.00000000 -137.26860000
5 0.02082400 8.92213100 3526.99 0.00000000 -137.34470000
6 0.00000000 0.00000000 3526.99 0.00000000 0.43010000
But the interesting observation is when I did Single Point calculation of that images I got different Relative energies, as follows:
0 0.0
1 1.2331
2 1.38191
3 2.18835
4 1.69337
5 1.67068
6 0.430029
My INCAR parameters are:
IVDW = 12 (DFT-D3 method of method with no damping)
LDAU = .TRUE. (Activate DFT+U)
LDATYPE= 2 (Dudarev; only U-J matters)
LDAUL = -1 -1 -1 2 (Orbitals for each species)
LDAUU = 0 0 0 0 5 (U for each species)
LDAUJ = 0 0 0 0 0 (J for each species)
LMAXMIX= 4 (Mixing cut-off; 4-d, 6-f)
# Global Parameters
ISTART = 1 (Read existing wavefunction; if there)
ISPIN = 1 (Non-Spin polarised DFT)
ALGO = VF
LREAL = AUTO (Projection operators: automatic)
ENCUT = 400 (Cut-off energy for plane wave basis set, in eV)
PREC = Normal (Precision level)
LWAVE = .FALSE. (Write WAVECAR or not)
LCHARG = .FALSE. (Write CHGCAR or not)
ADDGRID= .TRUE. (Increase grid; helps GGA convergence)
ISYM = 0
LASPH = T !use for LDA+U, hybrid or meta-GGA in f- and 3d-elements
# Budged Elastic Band (NEB)
LCLIMB = .TRUE.
LTANGENT = .TRUE. (following Graeme Suggestion with lower setup)
IMAGES = 5 (#of images without 2 endpoints,#of nodes=#of images/divisible,nodesOfGgroup/image)
NSW = 500 (number of ionic steps)
ISMEAR = 0 (gaussian smearing method)
SIGMA = 0.05 (please check the width of the smearing)
IBRION = 3 (do MD with a zero time step)
POTIM = 0 (Zero time step so that VASP does not move the ions)
SPRING = -5.0 (spring force (eV/A2) between images)
LCLIMB = .TRUE. (turn on the climbing image algorithm)
ICHAIN = 0 (Indicates which method to run. NEB (ICHAIN=0) is the default)
IOPT = 1 (LBFGS = Limited-memory Broyden-Fletcher-Goldfarb-Shanno)
# Relaxation
NELM = 200 (Max electronic SCF steps)
NELMIN = 6 (Min electronic SCF steps)
EDIFF = 1E-07 (SCF energy convergence; in eV)
ISIF = 2 (Stress/relaxation: 2-Ions, 3-Shape/Ions/V, 4-Shape/Ions)
EDIFFG = -0.025
# Surface dipole corrections
IDIPOL=3 ! 3 is for surfaces
LDIPOL= T
Would you please help me to find source of strange relative energies?
Thanks!