[Wien] Counting the numer of electrons / slightly metallic tail crossing EF

[Hua Wu]

When plotting the DOS of the VB electrons, a large contribution at the 
interstitial region is simply missing. --H. Wu

On Thursday 17 February 2011 15:17, Son Won-joon wrote:
> Dear WIEN2k Gurus.
>
> I am a novice with WIEN2k calculations, and now doing some
> spin polarized GGA(+U) caculations of Gd-Halide systems.
>
> And I have some trivial (but annoying to me) questions:
>
> 1.
> When I check TOTAL CORE-CHARGE of Gd after lstart (and scf file),
>
>  TOTAL CORE-CHARGE:                   46.000000
>  TOTAL CORE-CHARGE INSIDE SPHERE:     45.999929
>  TOTAL CORE-CHARGE OUTSIDE SPHERE:     0.000071
>
> MAGNETIC MOMENT IN SPHERE seems quite reasonable,
> but I would like to make sure whether this order of charge leakage
> can be negligible in total energy calculations (with different spin
> configurations).
>
> I am using the default RMT and R0 values in my struct file.
> Gd        NPT=  781  R0=.000010000 RMT=   2.50000   Z:  64.00000
>
> 2.
> Also, in the end of outputst, OCCUPANCY and ENERGY(RYD) of Gd looks like
> ...
>  4D*     2.000    -1.1219532E+01
>  4D*     2.000    -1.0774702E+01
>  4D      3.000    -1.0797164E+01
>  4D      3.000    -1.0354003E+01
>  5S      1.000    -3.7282009E+00
>  5S      1.000    -3.4775735E+00
>  5P*     1.000    -2.2946120E+00
>  5P*     1.000    -2.0836248E+00
>  5P      2.000    -1.9680388E+00
>  5P      2.000    -1.7786762E+00
>  4F*     3.000    -7.9075700E-01
>  4F*     0.000    -3.9080067E-01
>  4F      4.000    -7.3468784E-01
>  4F      0.000    -3.3752094E-01
> ...
>
> Since I assigned the default -6.0 Ry for separating core and valence
> states, 5S and 5P come into my band states. so, I have 5S, 5P and 4F, 5D,
> 6S in my valence states.
>
> When I check NUMBER OF ELECTRONS(:NOE) in scf file
> as well as the TOTAL CORE-CHARGE of Gd, I can confirm that each
> Gd has total 18 e-'s in its band states, and QTL values also suggest
> Gd has 5s and 5p states occupied.
> And, estimation of the number of electrons from the sum of QTL values
> is ~ 85 % of :NOE, which I think reasonable.
>
> But when I run x tetra to draw the DOS plot, and check outputtdn/up files,
> the up+dn sum of the NUMBER OF ELECTRONS UP TO EF
> is about 61 % of the number from :NOE.
>
> Even though I exclude the 5S and 5P electrons (10 e-) from counting in
> :NOE, the number from NUMBER OF ELECTRONS UP TO EF is still smaller.
> Is it normal to have much smaller (like 2/3) values in outputtdn/up
> than that of :NOE? Or those two numbers are of different meaning?
>
> 3.
> When I plot the DOS, with settings in int file as
>  -0.500   0.00001   0.8  0.0005     #Emin, DE, Emax, Gauss-Broad
> this results in slight VBM tail crossing the EF.
>
> I expect from the simple electron countings,
> this system should shows the gap between VBM and CBM,
> suspecting this is solely due to the Gaussian broadening.
> (Even though I use the GGA+U scheme, this tail is still there.)
>
> So, I checked outputtup/dn file, and I find
> I have non-integer occupation number in up spin, like 195.9998, at EF
> and it sustains the decimal value upto the conduction band minimum.
> The down spin shows exact interger number of electrons up to EF.
>
> I would like to know whether the 0.0002 e- deficiency
> is due to the numerical error (thus can be neglected),
> or I should check with the band structure to determine the metallicity
> of the system.
>
> When the number from the outputtup/dn file suggests sort of band gap,
> then could I consider this system as a semi-conductor regardless of the
> metallic states tail in dos1up/dn files?
>
> And, if 0.0002 e- is due to the numerics,
> is there any way to remove this annoying number?
> (I am using RKMAX=8, GMAX=14, and quite large number of kpoints.)
>
> I am terribly sorry for bothering you,
> but I still hope you will give me a kind consideration.
>
> Many thanks in advance.
>
> Sincerely,
> Won-joon Son
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