Thank you very much Dr. Martin Pieper. Yes phonon calculations speak about stability of structure but not about breaking point.
On Mon, Dec 7, 2015 at 1:22 PM, pieper <pie...@ifp.tuwien.ac.at> wrote: > Hello Muhammad! > > A DFT code will not simply say *crack* at some point of strain. Wien2k > will always distribute the force you apply according to the perfect > translational symmetry of your crystal structure - in contrast to nature > where things like cracking or breaking occure at weak links - points where > this translational symmetry is broken and the bonding is weaker. > > DFT will do its very best to distribute the electrons in any structure you > throw at it and tell you (an upper bound of) the minimum energy of the > configuration. I am no expert but I understand that from a calculated > variation of total energy with lattice parameter you can estimate the > intrinsic strength of a structure within some model for the process. > > In addition Wien2k gives information where the total energy is stored, for > example the forces on atoms in your structure. Therefore, if you look at > the total energy of your strained structure you will see that it is larger > - at 5% distortion perhaps considerably so. Depending on site symmetry some > calculated internal forces may indicate where in the structure the > 'springs' you pulled are located. Furthermore the phonon code might inform > you of instabilities in your structure. > > Good luck, > > Martin Pieper > > > --- > Dr. Martin Pieper > Karl-Franzens University > Institute of Physics > Universitätsplatz 5 > A-8010 Graz > Austria > Tel.: +43-(0)316-380-8564 > > > > Am 04.12.2015 15:25, schrieb Muhammad Sajjad: > >> Dear Tomas and Fecher >> Thank you very much. It is working perfect with lattice type F and >> symmetry operations equal to 16. But one thing is confusing me that I >> applied 5 % strain to bulk Si and still it is semiconductor with gap >> 0.2eV. Is it correct? as 5 % is too much strain and bulk materials >> tolerate very low strain. In my thinking it should break. >> >> On Fri, Dec 4, 2015 at 5:14 PM, Fecher, Gerhard <fec...@uni-mainz.de> >> wrote: >> >> but your structure becomes tetragonal >>> you should reset the symmetry operations to (generate) to be >>> recalculated during initialisation >>> >>> Ciao >>> Gerhard >>> >>> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy: >>> "I think the problem, to be quite honest with you, >>> is that you have never actually known what the question is." >>> >>> ==================================== >>> Dr. Gerhard H. Fecher >>> Institut of Inorganic and Analytical Chemistry >>> Johannes Gutenberg - University >>> 55099 Mainz >>> and >>> Max Planck Institute for Chemical Physics of Solids >>> 01187 Dresden >>> ________________________________________ >>> Von: wien-boun...@zeus.theochem.tuwien.ac.at >>> [wien-boun...@zeus.theochem.tuwien.ac.at] im Auftrag von Muhammad >>> Sajjad [sajja...@gmail.com] >>> Gesendet: Freitag, 4. Dezember 2015 15:08 >>> An: A Mailing list for WIEN2k users >>> Betreff: Re: [Wien] Fwd: Strain >>> >>> I am sorry having no idea about it. Simply I used optimized >>> structure and increased a by a0*1.001 and decreased b & c by keeping >>> lattice type F. Then run init_lapw -b. >>> >>> On Fri, Dec 4, 2015 at 4:51 PM, Fecher, Gerhard >>> <fec...@uni-mainz.de<mailto:fec...@uni-mainz.de>> wrote: >>> you applied a tetragonal distortion along x >>> but how did you manage that you still have 48 symmetry operations ? >>> >>> Ciao >>> Gerhard >>> >>> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy: >>> "I think the problem, to be quite honest with you, >>> is that you have never actually known what the question is." >>> >>> ==================================== >>> Dr. Gerhard H. Fecher >>> Institut of Inorganic and Analytical Chemistry >>> Johannes Gutenberg - University >>> 55099 Mainz >>> and >>> Max Planck Institute for Chemical Physics of Solids >>> 01187 Dresden >>> ________________________________________ >>> Von: >>> >>> wien-boun...@zeus.theochem.tuwien.ac.at<mailto: >> wien-boun...@zeus.theochem.tuwien.ac.at> >> >>> >>> [wien-boun...@zeus.theochem.tuwien.ac.at<mailto: >> wien-boun...@zeus.theochem.tuwien.ac.at>] >> >>> im Auftrag von Muhammad Sajjad >>> [sajja...@gmail.com<mailto:sajja...@gmail.com>] >>> >>> Gesendet: Freitag, 4. Dezember 2015 14:04 >>> An: wien >>> Betreff: [Wien] Fwd: Strain >>> >>> Dear All >>> I got Si structure from wien2k examples and after optimization it >>> is >>> SILICON >>> F LATTICE,NONEQUIV.ATOMS: 1 >>> MODE OF CALC=RELA unit=ang >>> 10.305626 10.305626 10.305626 90.000000 90.000000 90.000000 >>> ATOM 1: X=0.12500000 Y=0.12500000 Z=0.12500000 >>> MULT= 2 ISPLIT= 2 >>> 1: X=0.87500000 Y=0.87500000 Z=0.87500000 >>> Si NPT= 781 R0=0.00010000 RMT= 2.22 Z: >>> 14.0 >>> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000 >>> 0.0000000 1.0000000 0.0000000 >>> 0.0000000 0.0000000 1.0000000 >>> 48 NUMBER OF SYMMETRY OPERATIONS >>> >>> mBJLDA gives band gap of 1.19 eV (perfect). >>> >>> Now I apply strain (0.1 %) and structure is >>> >>> SILICON >>> F LATTICE,NONEQUIV.ATOMS: 1 >>> MODE OF CALC=RELA unit=ang >>> 10.315932 10.300477 10.300477 90.000000 90.000000 90.000000 >>> ATOM -1: X=0.12500000 Y=0.12500000 Z=0.12500000 >>> MULT= 2 ISPLIT=-2 >>> -1: X=0.87500000 Y=0.87500000 Z=0.87500000 >>> Si NPT= 781 R0=0.00010000 RMT= 2.22 Z: >>> 14.0 >>> LOCAL ROT MATRIX: 0.0000000 0.0000000 1.0000000 >>> 1.0000000 0.0000000 0.0000000 >>> 0.0000000 1.0000000 0.0000000 >>> 48 NUMBER OF SYMMETRY OPERATIONS >>> This time band structure (attached herewith) is very different and >>> Si is metal. >>> Kindly guide me whether I am apply strain in right way or not? Band >>> Structure is >>> >>> Kind Regards >>> Muhammad Sajjad >>> Post Doctoral Fellow >>> KAUST, KSA. >>> _______________________________________________ >>> Wien mailing list >>> >>> Wien@zeus.theochem.tuwien.ac.at<mailto:Wien@zeus.theochem.tuwien.ac.at> >> >>> >>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien [1] >>> SEARCH the MAILING-LIST at: >>> >>> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html >> >>> [2] >>> >>> -- >>> Kind Regards >>> Muhammad Sajjad >>> Post Doctoral Fellow >>> KAUST, KSA. >>> _______________________________________________ >>> Wien mailing list >>> Wien@zeus.theochem.tuwien.ac.at >>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien [1] >>> SEARCH the MAILING-LIST at: >>> >>> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html >> >>> [2] >>> >> >> -- >> >> Kind Regards >> Muhammad Sajjad >> Post Doctoral Fellow >> KAUST, KSA. >> >> Links: >> ------ >> [1] http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> [2] >> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html >> >> _______________________________________________ >> Wien mailing list >> Wien@zeus.theochem.tuwien.ac.at >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> SEARCH the MAILING-LIST at: >> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html >> > _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html > -- Kind Regards Muhammad Sajjad Post Doctoral Fellow KAUST, KSA.
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