Thank you for your quick response. To create a dangling bond, I need to remove one atom of Cd (or S) form periodic CdS system. Is it correct method to create a Dangling bond? 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 10:28 PM Giuseppe Mattioli < [email protected]> wrote: > > 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" <[email protected]>: > > > 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 <[email protected]> > > 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 < > >> [email protected]> 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 <[email protected]>: > >>> > >>> > 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 > >>> > <[email protected]> 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) > >>> >> users mailing list [email protected] > >>> >> https://lists.quantum-espresso.org/mailman/listinfo/users > >>> > _______________________________________________ > >>> > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > >>> > users mailing list [email protected] > >>> > 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: <[email protected]> > >>> > >>> _______________________________________________ > >>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > >>> users mailing list [email protected] > >>> 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: <[email protected]> > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users >
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