### Identical inputs, different results at different cpu cluster

Posted:

**Wed May 09, 2018 12:07 pm**Hello everyone

I am currently calculating the bulk structure of CoF3 using PBE+U according to the Dudarev formulation. The cell is a rhombohedral one with two units of CoF3 in it. I have optimized the structure at my computer cluster #1 and wanted to do a frequency calculation at another cluster #2 for reasons of convenience. But when I use the optimized structure as the POSCAR and run a single-point SCF calculation at cluster #2, the E0 is higher: -.33626837E+02 at #2 vs. the reference calculation at #1: -.35146116E+02 - i.e. a difference of a whole 1.5 eV. By looking at the DOS, the #2 calculation falsely describes the system as a conductor. #1 gives a band gap of 2.8 eV.

I tested the two single-point calculations using identical input files INCAR, KPOINTS, POSCAR and POTCAR (by copy-pasting them). The only difference is the computer cluster they are running on and the core/node distribution. Does anyone have an idea what might be going wrong here? I am thankful for any replies

Best regards,

Stefan

Cpu details:

#1: aprun protocol, 8 nodes with 8 cores each

#2: mpirun protocol, 2 nodes with 8 cores each

Both systems run vasp 5.4.1 (vasp_std executable, i.e. non-collinear)

INCAR:

KPOINTS:

POSCAR:

I spare you the POTCAR but it is constructed from the standard PBE PAW's

I am currently calculating the bulk structure of CoF3 using PBE+U according to the Dudarev formulation. The cell is a rhombohedral one with two units of CoF3 in it. I have optimized the structure at my computer cluster #1 and wanted to do a frequency calculation at another cluster #2 for reasons of convenience. But when I use the optimized structure as the POSCAR and run a single-point SCF calculation at cluster #2, the E0 is higher: -.33626837E+02 at #2 vs. the reference calculation at #1: -.35146116E+02 - i.e. a difference of a whole 1.5 eV. By looking at the DOS, the #2 calculation falsely describes the system as a conductor. #1 gives a band gap of 2.8 eV.

I tested the two single-point calculations using identical input files INCAR, KPOINTS, POSCAR and POTCAR (by copy-pasting them). The only difference is the computer cluster they are running on and the core/node distribution. Does anyone have an idea what might be going wrong here? I am thankful for any replies

Best regards,

Stefan

Cpu details:

#1: aprun protocol, 8 nodes with 8 cores each

#2: mpirun protocol, 2 nodes with 8 cores each

Both systems run vasp 5.4.1 (vasp_std executable, i.e. non-collinear)

INCAR:

- Code: Select all
`SYSTEM = CoF3 PBE`

NCORE = 8

ISTART = 0

LWAVE = .FALSE.

ISMEAR = 0 ! -5=linear tetrahedron (semiconductor/insulator), 0=gaussian

SIGMA = 0.10 ! temperature

PREC = Medium

!NSW = 100 ! ionic steps

IBRION = -1 ! 1=use quasi-newton optimization 2=conjugate gradient, -1=no optimization

ISIF = 3 ! 3=relax ions, cell shape and cell volume

ENMAX = 850 ! use together with ISIF

!ISYM = -1

POTIM = 0.25

EDIFF = 1.0E-5

EDIFFG = -0.01

ENCUT = 700

ICHARG = 2 ! 1=restart, 2=from atom solutions, 11=don't change density

ISPIN = 2 ! 2=spin polarized calculation

LORBIT = 11

MAGMOM = 4 -4 0 0 0 0 0 0

LAECHG = .TRUE.

LDAU = .TRUE.

LDAUTYPE = 2 ! 2=Dudarev

LDAUL = 2 -1 ! angular quantum number of orbitals 1=p, 2=d, 3=f

LDAUU = 6.3 0.0

LDAUJ = 1.0 0.0

LDAUPRINT = 2

LMAXMIX = 4 ! use with Hubbard

KPOINTS:

- Code: Select all
`K-Points`

0

Monkhorst Pack

8 8 8

0 0 0

POSCAR:

- Code: Select all
`CoF3`

1.00000000000000

2.9515852336660924 0.0000000000000000 4.4095306744468550

-1.4757926168330462 2.5561477937949211 4.4095306744468550

-1.4757926168330462 -2.5561477937949211 4.4095306744468550

Co F

2 6

Direct

0.0000000000000000 0.0000000000000000 0.0000000000000000

0.5000000000000000 0.5000000000000000 0.5000000000000000

0.8486837912520073 0.6513162087479927 0.2500000000000000

0.2500000000000000 0.8486837912520073 0.6513162087479927

0.6513162087479927 0.2500000000000000 0.8486837912520073

0.1513162087479927 0.3486837912520073 0.7500000000000000

0.7500000000000000 0.1513162087479927 0.3486837912520073

0.3486837912520073 0.7500000000000000 0.1513162087479927

0.00000000E+00 0.00000000E+00 0.00000000E+00

0.00000000E+00 0.00000000E+00 0.00000000E+00

0.00000000E+00 0.00000000E+00 0.00000000E+00

0.00000000E+00 0.00000000E+00 0.00000000E+00

0.00000000E+00 0.00000000E+00 0.00000000E+00

0.00000000E+00 0.00000000E+00 0.00000000E+00

0.00000000E+00 0.00000000E+00 0.00000000E+00

0.00000000E+00 0.00000000E+00 0.00000000E+00

I spare you the POTCAR but it is constructed from the standard PBE PAW's