Convergence problem with VASP.5.2.11 for already converged (using VASP.4.6) geometry ???
Posted: Thu Aug 09, 2012 7:04 am
Dear Admin & VASP user,
It seems very strange that relaxed geometry which I obtained using VASP.4.6 (within 12 ionic and 12-25 electronic steps in each ionic step) does not converge within 120 steps if I use VASP.5.2.11 (parallel).
Due to memory issues I can not do DOS calculation on serial clusters. For parallel calculation I take same INCAR, KPOINTS, POTCAR . I use CONTCAR of serial version as POSCAR of parallel version. I wanted to obtain only CHGCAR so that I can run DOS calculation. But convergence is very poor. I am taking already converged geometry. But with VASP.5.2.11 (||) after 120 steps instead of 10^-5 it reaches upto 10^-1. Convergence problem usually appears when the initial geometry is not correct. Which is not the case here. Then
?
I'm not understanding what is causing problem. Please suggest me how to handle this problem. I'll be be very thankful to you.
======================================================================
INCAR
Start parameter for this run:
ISTART = 0
ICHARG = 2
Electronic Relaxation 1
PREC = ACCURATE
ENCUT = 500
IALGO = 38 algorithm
NELM = 120 number of electronic steps between two ionic steps
NELMIN = 0
NELMDL = 3
EDIFF = 1E-05
GGA = PE
ISPIN = 2
MAGMOM= 1 1 1 1 3.5 1 1 1 1 1 1 1 1 1 1 1
LORBIT = 11
ADDGRID = .TRUE
LMAXMIX = 4
INIMIX = 0
AMIX = 0.2
BMIX = 0.0001
AMIX_MAG= 0.8
BMIX_MAG= 0.0001
MAXMIX = -12
Ionic Relaxation
NSW = 60 number of steps for IOM #
NBLOCK = 1
KBLOCK = 5 inner block; outer block
IBRION = 1
ISIF = 2
ISYM = 2 ! 1 for us-pp, 2 for PAW data sets are used
IWAVPR = 1
LCORR = T Harris-correction to forces
EDIFFG = -5.E-03 stopping-criterion for IOM
POTIM = .75 time-step for ion-motion
DOS related values:
SIGMA = 0.1; ISMEAR = -5 broad. in eV, -4-tet -1-fermi 0 gaus
Electronic Relaxation 2
LDIAG = T sub-space diagonalisation
NBANDS = 128
=====================================================================
best regards,
PS
It seems very strange that relaxed geometry which I obtained using VASP.4.6 (within 12 ionic and 12-25 electronic steps in each ionic step) does not converge within 120 steps if I use VASP.5.2.11 (parallel).
Due to memory issues I can not do DOS calculation on serial clusters. For parallel calculation I take same INCAR, KPOINTS, POTCAR . I use CONTCAR of serial version as POSCAR of parallel version. I wanted to obtain only CHGCAR so that I can run DOS calculation. But convergence is very poor. I am taking already converged geometry. But with VASP.5.2.11 (||) after 120 steps instead of 10^-5 it reaches upto 10^-1. Convergence problem usually appears when the initial geometry is not correct. Which is not the case here. Then
?I'm not understanding what is causing problem. Please suggest me how to handle this problem. I'll be be very thankful to you.
======================================================================
INCAR
Start parameter for this run:
ISTART = 0
ICHARG = 2
Electronic Relaxation 1
PREC = ACCURATE
ENCUT = 500
IALGO = 38 algorithm
NELM = 120 number of electronic steps between two ionic steps
NELMIN = 0
NELMDL = 3
EDIFF = 1E-05
GGA = PE
ISPIN = 2
MAGMOM= 1 1 1 1 3.5 1 1 1 1 1 1 1 1 1 1 1
LORBIT = 11
ADDGRID = .TRUE
LMAXMIX = 4
INIMIX = 0
AMIX = 0.2
BMIX = 0.0001
AMIX_MAG= 0.8
BMIX_MAG= 0.0001
MAXMIX = -12
Ionic Relaxation
NSW = 60 number of steps for IOM #
NBLOCK = 1
KBLOCK = 5 inner block; outer block
IBRION = 1
ISIF = 2
ISYM = 2 ! 1 for us-pp, 2 for PAW data sets are used
IWAVPR = 1
LCORR = T Harris-correction to forces
EDIFFG = -5.E-03 stopping-criterion for IOM
POTIM = .75 time-step for ion-motion
DOS related values:
SIGMA = 0.1; ISMEAR = -5 broad. in eV, -4-tet -1-fermi 0 gaus
Electronic Relaxation 2
LDIAG = T sub-space diagonalisation
NBANDS = 128
=====================================================================
best regards,
PS