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) > users mailing list users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users _______________________________________________ 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