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STM images

Posted: Tue Sep 25, 2007 3:52 pm
by simoneca
Hi,

I am trying to produce a simulated STM image from a converged spin polarized charge density. I know that p4vasp has this kind of feature but needs the PARCHG file. Probably it is not the best way to have STM images but is still the only on I know...(any suggestions for a newcomer in this field?)
I have tried to produce it using a preconverged WAVECAR and

ALGO = Fast
NELMIN = 8
EDIFF = 1E-6
ENCUT = 500
PREC = Accurate
LREAL = Auto
ISMEAR = -5
SIGMA = 0.2
ISPIN = 2

LPARD = .TRUE.
LSEPB = .FALSE.
LSEPK = .FALSE.

NSW = 0

LWAVE = .TRUE.
LCHARG = .TRUE.
NEDOS = 301
EMIN = -25
EMAX = 10
RWIGS = 0.77 0.37
LELF = .TRUE.
LORBIT = 5

but I haven't PARCHG at the end. Have I done something wrong ? I have not found anything about in the guide....
Do you know what kind of method p4vasp uses for this? Maybe Bardeen method?

Thanks in advance.

STM images

Posted: Wed Sep 26, 2007 1:49 pm
by admin
please read the chapter 'Band decomposed charge density' in the online handbook: if you just set LPARD, ( and none of the other parameters, or the others to false), the output charge is written to CHGCAR.
In your case (STM), you should define the energy range which contributes to states that give the tunneling current. This range is
given by the applied bias voltage (please read the Tersoff- Hamann paper): In addition to LPARD, EINT should be defined.