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Negative Charge Density in Ge PAWLDA problem
Posted: Mon May 26, 2008 5:07 am
by kundog00
I calculated Ge 2x2x2 supercell (64 atoms) with PAWLDA and in CHGCAR there are lots of negative charge densities are found. As I draw CHGCAR with VESTA program, it was observed that negative charges are loacated in the center of atom position. Is this problem caused by POTCAR file? I mean, pseudopotential may cause negative charge density? In Cu and Fe, HfO2, TiC results I didn't observe this happening. Plz give me any idea about this problem. I'll really appreciate about any comments or ideas on it. Thanks.
Ge is diamond cubic structure, Ecut = 300eV, Kpoints 6 6 6, RWIGS 1.217, spin off, lattice parameter 5.646 (optimized).
If you need any more calculation detail, plz let me know.
<span class='smallblacktext'>[ Edited ]</span>
Negative Charge Density in Ge PAWLDA problem
Posted: Thu May 29, 2008 11:45 am
by admin
Dear colleague, I don't know how VESTA processes the CHGCAR file in order to obtain the charge density plots, but most probably the reason for the negative charge densities near the core is the following:
the first block of data written in CHGCAR (L*M*N entries, where L,M and N are the 3 integer numbers written after the ionic positions) contains the pseudovalence total charge, which can be negative near to the core because of the on-site correction terms.
--the pseudized core charge can be included on the PW grid, to avoid numerical instabilities of E_xc[n_v(r)+ n_c(r)].
Negative Charge Density in Ge PAWLDA problem
Posted: Thu Sep 10, 2009 9:56 am
by xtra2000
I encountered the same question in Si. How could I avoid it? Any comments will be appreciated.
Negative Charge Density in Ge PAWLDA problem
Posted: Fri Nov 25, 2011 8:38 pm
by Danny
[quote="admin"]Dear colleague, I don't know how VESTA processes the CHGCAR file in order to obtain the charge density plots, but most probably the reason for the negative charge densities near the core is the following:
the first block of data written in CHGCAR (L*M*N entries, where L,M and N are the 3 integer numbers written after the ionic positions) contains the pseudovalence total charge, which can be negative near to the core because of the on-site correction terms.
--the pseudized core charge can be included on the PW grid, to avoid numerical instabilities of E_xc[n_v(r)+ n_c(r)].
[/quote] pseudovalence total charge[/b] defined in the CHGCAR? Is this the chargedensity as calculated from the wavefunction obtained in VASP and then minus the chargedensity due to the pseudo-onsite radial grids?
Or something else?
I'm very confussed on this point.
Danny