[Wien] [SPAM?] Re: Counting the numer of electrons / slightly metallic tail crossing EF

[Son Won-joon]

Dear Professor Wu and Professor Blaha.

I truly appreciate your kind advice.

I am truly happy to be confirmed that
I could consider this 0.0002 e- deviation from the integer number of
electrons as negligible.

Thank you.

On Fri, Feb 18, 2011 at 5:17 PM, Peter Blaha
<pblaha at theochem.tuwien.ac.at> wrote:
>> 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).
>
> This is perfectly ok and you don't have to worry.
>
>> 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?
>
> Probably your Emin (-0.5 )in case.int is not ok and you are truncating some
> DOS (F 2s ?)
>
>> 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
>
> With such DE you are "asking" for numerical inaccuracies.
> Stick to the defaults first or modify them only slighly.
>
> For sure "Gauss-broadening" introduces some small tails above EF which are
> of course artifacts due to the broadening.
>
>> 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?
>
>
> --
> Peter Blaha
> Inst.Materials Chemistry
> TU Vienna
> Getreidemarkt 9
> A-1060 Vienna
> Austria
> +43-1-5880115671
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