[QE-users] Soft Hydrogen Pseudopotentials

[Giuseppe Mattioli]

> I believe fractional charge H atoms would not be useful for these  
> kinds of materials. Right?

I suppose you are right. I can only suggest you to double check the  
results and to carefully compare with experimental results obtained on  
real systems. I cited C-diamond, which is "akin" to Si and Ge, because  
surface hydrogenation induce a large upward shift of both valence and  
conduction bands, measured by ARPES and compared with DFT calculations  
here: Phys. Rev. B 94, 045307 (2016)

Surface or interstitial H is a well known dopant in semiconductors.  
Among tons of papers (I'm ashamed to cite mine :-)) I can suggest the  
classical Van de Walle Nature paper on universal alignment of H  
(Nature 423, 626, 2003)

HTH
Giuseppe

Quoting Matthieu Fortin-Deschênes <matthieu.fortin-deschenes at polymtl.ca>:

> Thanks Giuseppe,
>
> I actually want to passivate the bottom of Si and Ge surfaces, as  
> well as one edge of a 2D nanoribbon (antimonene).
> I believe fractional charge H atoms would not be useful for these  
> kinds of materials. Right?
>
> I was not aware of this strong dopant effect, but I'd be interested  
> in reading more about it if you have any reference to suggest.
>
> Thank you,
>
> Matthieu
>
> Giuseppe Mattioli <giuseppe.mattioli at ism.cnr.it> a écrit :
>
>> Dear Matthieu
>> I don't know which surface you want to passivate, but remember that  
>> H can also have a strong dopant effect on surfaces (e.g., a large  
>> upward shift of both band edges, which has been measured on  
>> C-diamond). Therefore, I used to passivate the unreconstructed end  
>> of III-V slabs with *pseudo* H atoms, having fractional charge  
>> which simulate a bulk environment surrounding the bottom layer of  
>> the slab. They used to be in the online library but they are not  
>> anymore (maybe for good reasons which I don't know). If you want to  
>> try I can send you the UPF files. They are NC VBC pseudopotentials  
>> which should not require more than ecutwfc=40: after all you are  
>> not interested in structural rearrangement but you only need  
>> electronic passivation of surface states.
>> HTH
>> Giuseppe
>>
>> Quoting Matthieu Fortin-Deschênes <matthieu.fortin-deschenes at polymtl.ca>:
>>
>>> Hi all,
>>>
>>> I want to use hydrogen to passivate the bottom surface of a  
>>> surface slab. However, I notice that H PPs usually require a high  
>>> ecutwfc, which restricts the size of the system I can consider.
>>>
>>> Are there any PPs with lower required ecutwfc available for that purpose?
>>> And would this negatively effect the accuracy of the calculations  
>>> on the other side of the surface slab?
>>>
>>> Thank you,
>>>
>>> Matthieu Fortin-Deschênes
>>> Polytechnique Montréal
>>>
>>> _______________________________________________
>>> users mailing list
>>> users at lists.quantum-espresso.org
>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>
>>
>>
>> GIUSEPPE MATTIOLI
>> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
>> Via Salaria Km 29,300 - C.P. 10
>> I-00015 - Monterotondo Scalo (RM)
>> Mob (*preferred*) +39 373 7305625
>> Tel + 39 06 90672342 - Fax +39 06 90672316
>> E-mail: <giuseppe.mattioli at ism.cnr.it>
>>
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>
>
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GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
Via Salaria Km 29,300 - C.P. 10
I-00015 - Monterotondo Scalo (RM)
Mob (*preferred*) +39 373 7305625
Tel + 39 06 90672342 - Fax +39 06 90672316
E-mail: <giuseppe.mattioli at ism.cnr.it>