[Pw_forum] Question about electron (pseudo-)charge density calculations in QE
rezavatan64 at gmail.com
Thu May 26 21:56:16 CEST 2016
Dear Paolo and Stefano,
Thank you so much for your reply.
Both ways give me the same values but still incorrect value which is 8
electron per unit cell however I have only 2 electron per unit cell. Is it
possible that QE is giving me charge density in a unit different than
Paolo! I only have one hydrogen molecule per unit cell. Following is my
outdir = './',
ibrav = 6, celldm(1) =20.37, celldm(3) =1.0, nat =2, ntyp=1,
ecutwfc = 12.0,
ecutrho = 100,
degauss = 0.05D0,
occupations = "fixed",
smearing = "methfessel-paxton",
H 1.01 Si.blyp-hgh.UPF
H 0.099985299 0.099985299 0.077144425
H 0.100014701 0.100014701 0.862855575
4 4 4 0 0 0
On Wed, May 25, 2016 at 10:40 PM, Stefano de Gironcoli <degironc at sissa.it>
> Dear Reza Vatan,
> In order to canculate the total charge you should sum the density on
> all point and multiply the result by the volume element. That is multiply
> by 20.37^3 and divide by 45^3 or 72^3 depending on the grid used.
> Which gives 8 in both cases
> Di you place 4 molecules in the unit cell ?
> (sent from my phone)
> > On 26 May 2016, at 01:44, reza vatan <rezavatan64 at gmail.com> wrote:
> > Dear all,
> > I have one hydrogen molecule in a unit cell repeating in 3D space in
> such a way non of the hydrogen molecules can't see each other. I'm trying
> to calculate the "electron (pseudo-)charge density" in the entire unit cell
> using pp.x. The problem is that when I add the charge density of all meshes
> to get the total charge density of the entire unit cell I get different
> values depends on the used grid. For instance, when I use 45x45x45 grid I
> get 86.25 for charge density, but when I use 72x72x72 I get 353.26.
> > However, since my unit cell size is 20.37x20.37x20.37 bhor^3 and I have
> 2 electrons in the unit cell, I think I should get
> 2/(20.37x20.37x20.37)=0.000236623. Does any one know why I'm not getting
> this number?
> > Thanks in advances,
> > Best,
> > Reza Vatan,
> > Electrical Engineering Department,
> > Arizona State University.
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