[Wien] Spin-orbit coupling effect on band gap energy with LDA and GGA-PBE
Peter Blaha
peter.blaha at tuwien.ac.at
Fri May 17 07:25:34 CEST 2024
As I said before:
The first question is: why is LDA+mBJ and PBE#mBJ not identical ??
What is :DIS of all your calculations ?
My guess is that they are not converged (just 40 default iterations,
just default convergence ?)
We do not know enough about your compound (except that it contains Bi),
but this does not happen in 99.9 % of all cases.
The behavior with SO is a second step, but unless the first one is
solved, I would not even discuss the SO behavior.
Also your comment about EMAX=6 (which is a very small increase for a
convergence test) indicates to me, that the previous calculations have
not been converged.
Am 16.05.2024 um 21:59 schrieb Yakup Boran:
> Dear Dr. Blaha,
>
> 1. Case: I get 4.85 eV for LDA and then MBJ without SO (4.77 eV with SO)
>
> 2. Case: I get 4.74 eV for PBE and then MBJ without SO (4.79 eV with SO)
>
> In the 1. case band gap decreases with SO, but in the 2. case band gap
> increases.
>
> I use Emax=5 eV for both calculations.
>
> As far as I know, for SO calculation Emax should be chosen carefully. I
> did another calculation with Emax = 6eV.
>
> This time, in both cases, the band gap increases with SO.
>
> In literature, band gap decrease is expected with SO, but I get band gap
> increase in my calculations.
>
> My question is if there is something else should I check. Or how one
> can explain the band gap increase?
>
> Best regards.
>
> On Sat, May 11, 2024 at 7:14 PM Peter Blaha <peter.blaha at tuwien.ac.at
> <mailto:peter.blaha at tuwien.ac.at>> wrote:
>
> __
>
> Do you get identical gaps for:
>
> LDA and then MBJ (no SO)
>
> PBE and then MBJ (no SO) ???
>
> If you did everything right, there is no reason why adding SO at the
> end should give a different result.
>
> Probably some other mistake ... ?
>
>
> Am 11.05.2024 um 17:32 schrieb Yakup Boran:
>> Dear Dr Blaha,
>>
>> I think I did not write clear enough.
>>
>> The calculation was done by following:
>>
>> 1. I did regular scf calculation with LDA
>> 2. I added mBJ on it.
>> 3. Then I added SOC.
>>
>> I repeated the same calculation with PBE.
>>
>>
>> Thank you
>>
>> 11 May 2024 Cmt, saat 17:08 tarihinde Peter Blaha
>> <peter.blaha at tuwien.ac.at <mailto:peter.blaha at tuwien.ac.at>> şunu
>> yazdı:
>>
>> No.
>>
>> These 2 calculations should be exactly the same.
>>
>> What matters is only: XC_MBJ
>>
>> Everything in parenthesis is only a comment to give you a few
>> common options.
>>
>>
>> Am 11.05.2024 um 16:00 schrieb Yakup Boran:
>>> Dear Dr Blaha,
>>>
>>> Thank you for your response.
>>>
>>> ———————————
>>> case.in0 for LDA is
>>>
>>> TOT XC_MBJ ( (XC_PBE,XC_PBESOL,XC_WC,XC_MBJ,XC_SCAN)
>>>
>>> R2V IFFT (R2V)
>>>
>>> 30 30 48 2.00 1 NCON 9 # min IFFT-parameters, enhancement
>>> factor, iprint, NCON n
>>>
>>> ——————————-
>>> Case.in0 for PBE
>>>
>>> TOT XC_MBJ ( (XC_LDA,XC_PBESOL,XC_WC,XC_MBJ,XC_SCAN)
>>> R2V IFFT (R2V)
>>>
>>> 30 30 48 2.00 1 NCON 9 # min IFFT-parameters, enhancement
>>> factor, iprint, NCON n
>>>
>>> ———————-
>>>
>>> Best regards
>>>
>>> 11 May 2024 Cmt, saat 16:03 tarihinde Peter Blaha
>>> <peter.blaha at tuwien.ac.at <mailto:peter.blaha at tuwien.ac.at>>
>>> şunu yazdı:
>>>
>>> I'm not quite sure I understand what you did.
>>>
>>> You are always using mBJ (for VX), but how do you mix
>>> in LDA or PBE ?
>>>
>>> By default we use LDA for VC, (and anything for EX and
>>> EC, since this is
>>> not important).
>>>
>>> Usually, the choice of VC has only a small effect (as
>>> compared to VX).
>>>
>>> Please show the 2 lines in case.in0
>>>
>>>
>>> Am 10.05.2024 um 15:56 schrieb Yakup Boran:
>>> > Dear Wien2K users,
>>> > I am running a calculation for a Bi-containing compound
>>> with a
>>> > tetragonal structure type. I used LDA with mBJ, and
>>> then, due to the
>>> > heavy Bi atom, I did the SOC calculation. The
>>> calculated band gap
>>> > energy with SOC is smaller than without SOC. I checked
>>> the literature,
>>> > and the band gap decrease is common for SOC
>>> calculation. However, if I
>>> > use PBE-GGA with mBJ (instead of LDA with mBJ), the
>>> band gap energy
>>> > with SOC is greater than without SOC, which is contrary
>>> to the
>>> > literature.
>>> >
>>> > Is it possible that I get a band gap decrease with LDA
>>> while I get a
>>> > band gap increase with PBE-GGA when the SOC effect is
>>> taken into
>>> > consideration?
>>> >
>>> > Any response will be appreciated.
>>> >
>>> > Best Regards
>>> >
>>> > Yakup Bran
>>> >
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>>> --
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>>> Peter Blaha, Inst. f. Materials Chemistry, TU Vienna,
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>>
>> --
>> -----------------------------------------------------------------------
>> Peter Blaha, Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
>> Phone: +43-158801165300
>> Email:peter.blaha at tuwien.ac.at <mailto:peter.blaha at tuwien.ac.at>
>> WWW:http://www.imc.tuwien.ac.at <http://www.imc.tuwien.ac.at> WIEN2k:http://www.wien2k.at <http://www.wien2k.at>
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>>
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>
> --
> -----------------------------------------------------------------------
> Peter Blaha, Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-158801165300
> Email:peter.blaha at tuwien.ac.at <mailto:peter.blaha at tuwien.ac.at>
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