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How to start MD calculation?

Posted: Sat Jun 30, 2007 7:11 am
by Jiaye Li
Dear support

I want to run MD calculations with vasp under coarse criterion. The pressure, number and temperature need to be fixed. This is my INCAR:

Startparameter for this run:
NWRITE = 2 write-flag & timer
PREC = low medium, high low
ISTART = 0 job : 0-new 1-cont 2-samecut
ICHARG = 2 charge: 1-file 2-atom 10-const
ISPIN = 1 spin polarized calculation?
Electronic Relaxation 1
ENCUT = 250.0 eV
NELM = 60; NELMIN= 8; NELMDL=-8 # of ELM steps
EDIFF = 0.1E-04 stopping-criterion for ELM
LREAL = A real-space projection
Ionic relaxation
EDIFFG = 0.1E-03 stopping-criterion for IOM
NSW = 500 ------- Is it usefull for MD???
IBRION = 0 ionic relax: 0-MD 1-quasi-New 2-CG
NBLOCK = 1
NFREE = 2 steps in history (QN), initial steepest desc. (CG)
ISIF = 2 stress and relaxation
ISYM = 0 0-nonsym 1-usesym 2-fastsym

POTIM = 3.00 ------------ Does it mean 3 fs???
TEBEG = 300.0; TEEND = 300.0 temperature during run --------------------Does it mean the temperature will be 300K during calculation???
SMASS = 2.00 Nose mass-parameter (am)
! PSTRESS= 0.0 ---------How to control the pressure???

DOS related values:
EMIN = 10.00; EMAX =-10.00 energy-range for DOS
ISMEAR = 0; SIGMA = 0.20 broadening in eV -4-tet -1-fermi 0-gaus

Electronic relaxation 2 (details)
GGA= 91
IALGO = 48 algorithm
BMIX = 2.0
LDIAG = T sub-space diagonalisation
! IMIX = 4 mixing-type and parameters
! AMIX = 0.20; BMIX = 0.0001
! AMIX_MAG = 0.80; BMIX_MAG = 0.0001
! AMIN = 0.10
! WC = 1000; INIMIX= 1; MIXPRE= 1
! TIME = 0.10 timestep for ELM

Write flags
LWAVE = T write WAVECAR
LCHARG = T write CHGCAR
LVTOT = T write LOCPOT, local potential
LORBIT = 10
Dipole corrections
IDIPOL = 0 1-x, 2-y, 3-z
LDIPOL = F correct potential


Is my INCAR correct?
Thanks!

How to start MD calculation?

Posted: Mon Jul 02, 2007 7:29 am
by admin
1) MD can only be run for constant V
2) your input:
--) NSW=500 is reasonable, you can continue with a second MD run if you keep WAVECAR and re-start with CONTCAR (out, run N) as new POSCAR (in, run N+1)
--) it makes no sense to choose ISIF=2 for a low-PREC calculation, please use the dafault value (ISIF=0 for IBRION=0)
--) in general, it is safer to set ALGO=Fast instead of IALGO=48
--) it makes no sense to set LVTOT in a MD run
--) the instantaneous T is calculated from the kinetic energies of the atoms, so it may fluctuate around 300 K.
--) POTIM is the time step in fs, you are right.
all other parameters seem reasonable as far as one can say without knowing the details of your system.

How to start MD calculation?

Posted: Wed Jul 04, 2007 9:02 am
by Jiaye Li
Thank you very much. I made changes accordingly before submitting the jobs.