Dear Kumar
In your attached file there is a correct and fully periodic CdS
zincblend structure. I don't see any dangling bond.
>> I have one more question. Is it sufficient to remove one atom Cd (or S)
form CdS crystal
To obtain what?
i need to modify/regenerate pseudo-potential file
to calculate properties related to Dangling bond during DFT simulation?
No, you don't
HTH
Giuseppe
Quoting "Dr. SUNIL KUMAR" <suniliit...@gmail.com>:
I have carried out some dft simulations as attached file.
Dr. Sunil Kumar
Ph.D (Chemical Engg. IIT Delhi)
M.Tech (Chemical Engg. IIT Delhi)
B.Tech (Chemical Engg. IET-CSJMU Kanpur)
Scientist-C and Assistant Professor
CSIR-National Metallurgical Laboratory Jamshedpur-831007
http://www.nmlindia.org/
https://scholar.google.co.in/citations?user=OchYqugAAAAJ&hl=en&oi=sra
On Thu, Nov 12, 2020 at 10:10 PM Dr. SUNIL KUMAR <suniliit...@gmail.com>
wrote:
Thankyou for your explanation regarding Dangling bond.
I have one more question. Is it sufficient to remove one atom Cd (or S)
form CdS crystal or also i need to modify/regenerate pseudo-potential file
to calculate properties related to Dangling bond during DFT simulation?
thanks
Dr. Sunil Kumar
Ph.D (Chemical Engg. IIT Delhi)
M.Tech (Chemical Engg. IIT Delhi)
B.Tech (Chemical Engg. IET-CSJMU Kanpur)
Scientist-C and Assistant Professor
CSIR-National Metallurgical Laboratory Jamshedpur-831007
http://www.nmlindia.org/
https://scholar.google.co.in/citations?user=OchYqugAAAAJ&hl=en&oi=sra
On Thu, Nov 12, 2020 at 8:53 PM Giuseppe Mattioli <
giuseppe.matti...@ism.cnr.it> wrote:
Dear Tamas and Kumar
only to add a few words to the (very pertinent) Tamas' reply:
1) Semiconductor surfaces can undergoes very complex reconstruction
patterns (the 7x7 Si(111) reconstruction being likely the most famous
case). You will not find complex reconstructions by simply cutting and
relaxing the slabs, and it is best to search in experimental
literature, in order not to waste time simulating unphysical systems
which are never going to converge.
2) Dangling bonds can be also created inside crystals (e.g, by atomic
vacancies). It is not clear what kind of dangling bond you are
referring to.
3) There is an additional problem when you want to simulate some
process happening on the surface (e.g., adsorptions of molecules).
Various strategies can be used, including the saturation of dangling
bonds on one side of the slab by "pseudohydrogen atoms" having
fractional charge mimicking that of the pristine bond broken by
cleavage.
This said, you should "make an educated guess" [cit. John Malkovich
:-)] and ask less general questions which may (or may not) generate
more useful answers.
HTH
Giuseppe
Quoting Tamas Karpati <tkarp...@gmail.com>:
> Dear Dr. Kumar,
>
> I guess dangling bonds are written about in DFT textbooks of the
> physicists' style
> (in quantum chemistry, ie. clusters rather than crystals, it is less
> of a problem).
>
> The typical problem is that you cut chemical bonds when cleave the
> crystal (to get a slab).
> In case of bonds originally dominated by ionic (Coulomb) forces you
> may still have a closed
> shell system (ie. just paired electrons) after the cleavage. As for
> the more covalent
> bonds, radicals are generated and such high multiplicity electronic
> states (large
> magnetizations in terms of QE/PW.x inputs) reorganize to the more
> stable closed
> shell systems by changing geometry (you need to reoptimize their
> geometry) and
> simultaneously forming new bonds. This way every few surface atom
> pairs get closer
> and such bonds form, ie. bonds that were dangling after you made the
> cut are now
> in covalent bonds again (no dangling anymore).
> This you can model by reoptimizing with low (not sure but probably
> zero) magnetization.
>
> CdS has strong bonds carrying both ionic (maybe less) and covalent
nature
> (more of the latter). Depending on the cleaving plane you applied to
> the crystal,
> you have a high chance to see new Cd-S bonds form. Less probable is
> that you'll
> have Cd-Cd bonds or -S-S- bridges but these are also possible if your
surface
> atoms are situated so.
>
> Another way of treating such systems is to keep the structure as you
have cut
> from the crystal and apply a high starting_magnetization in a PW/relax
job.
>
> Be careful, though, as the chemistries you describe by the above two
methods
> (reorganization vs. high magnetization) are living in two distant
Universes.
>
> I hope this helps,
> Tamas
>
> On Thu, Nov 12, 2020 at 8:13 AM Dr. SUNIL KUMAR
> <suniliit...@gmail.com> wrote:
>>
>> Dear QE developers and Users.
>> I am struggling to carry out a DFT simulation of CdS with dangling
>> bonds using Quantum Espresso DFT packages. I am unable to
>> understand the phenomena of Dangling bond and its implementation in
>> QE DFT simulation. I would like to request to you all, kindly
>> suggest me some tutorial and sample QE scripts for CdS with
>> Dangling bonds. I will be grateful to you.
>>
>> Thanks
>> With regards
>> SUNIL
>> Dr. Sunil Kumar
>> Ph.D (Chemical Engg. IIT Delhi)
>> M.Tech (Chemical Engg. IIT Delhi)
>> B.Tech (Chemical Engg. IET-CSJMU Kanpur)
>> Scientist-C and Assistant Professor
>> CSIR-National Metallurgical Laboratory Jamshedpur-831007
>> http://www.nmlindia.org/
>> https://scholar.google.co.in/citations?user=OchYqugAAAAJ&hl=en&oi=sra
>>
>> _______________________________________________
>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
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> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users@lists.quantum-espresso.org
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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.matti...@ism.cnr.it>
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list users@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.matti...@ism.cnr.it>
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list users@lists.quantum-espresso.org
https://lists.quantum-espresso.org/mailman/listinfo/users
