Dear Sir, I understand your point. I am using PBE functional. I am still in doubt, which lattice parameter I should use for the rest of the properties. Thanks
On Fri, Sep 17, 2021 at 5:11 PM Laurence Marks <[email protected]> wrote: > That means that the cubic phase is not stable at T=0 for the functional > you have chosen. This may be correct or incorrect, it is not uncommon (e.g. > SrTiO3 with PBE). > > _____ > Professor Laurence Marks > "Research is to see what everybody else has seen, and to think what nobody > else has thought", Albert Szent-Györgyi > www.numis.northwestern.edu > > On Fri, Sep 17, 2021, 06:37 fatima DFT <[email protected]> wrote: > >> Thanks Sir >> No Sir!!! >> I mean, the original system is lower in energy but the phonon band >> structure has some soft modes. >> When I apply a compressive strain, the soft mode disappears. >> I am sorry if you found my previous query a bit confusing. >> >> Thanks >> Fatima >> >> >> >> On Fri, Sep 17, 2021 at 5:01 PM Laurence Marks <[email protected]> >> wrote: >> >>> If I understand you correctly, your system is lower in energy for a >>> slightly smaller lattice parameter. This is not unusual, and depends upon >>> what functional you use. It is standard to calculate using the cell >>> parameters that minimize the dft energy. >>> >>> Is this right? What is the relevance of "right"? Doing phonons for a non >>> dft-equilibrium cell is obvious GIGO. Beyond that to band etc there is no >>> "right". >>> >>> _____ >>> Professor Laurence Marks >>> "Research is to see what everybody else has seen, and to think what >>> nobody else has thought", Albert Szent-Györgyi >>> www.numis.northwestern.edu >>> >>> On Fri, Sep 17, 2021, 06:22 fatima DFT <[email protected]> wrote: >>> >>>> I want to extend my question for band, doss, optical properties as well. >>>> >>>> One important thing is that the total energy is more negative for the >>>> original system by 0.65 eV when I apply 2.5% compressive strain and 2.8 eV >>>> when I apply 5% compressive strain. >>>> >>>> Thanks >>>> >>>> >>>> On Fri, Sep 17, 2021 at 3:33 PM fatima DFT <[email protected]> >>>> wrote: >>>> >>>>> Dear All, >>>>> >>>>> I am dealing with a cubic 3D perovskite system. >>>>> With its original lattice parameters, the system shows negative >>>>> frequencies. >>>>> At some 1% lattice strain, the system becomes dynamically stable >>>>> (no +ve frequency). >>>>> >>>>> My question is: Should I calculate elastic constant at the lattice >>>>> parameters where the system is dynamically stable or should I consider the >>>>> case with its original lattice parameters (fully optimized geometry with >>>>> no >>>>> strain)? >>>>> >>>>> >>>>> Thank you >>>>> Fatima >>>>> >>>> _______________________________________________ >>>> Wien mailing list >>>> [email protected] >>>> >>>> https://urldefense.com/v3/__http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien__;!!Dq0X2DkFhyF93HkjWTBQKhk!CU-q4QLnagFyEv62yxcAvl8Kfi5TLM-08F260z_aYMEY99K8U8ECAO3K3s3jWBg6hGRtqQ$ >>>> SEARCH the MAILING-LIST at: >>>> https://urldefense.com/v3/__http://www.mail-archive.com/[email protected]/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!CU-q4QLnagFyEv62yxcAvl8Kfi5TLM-08F260z_aYMEY99K8U8ECAO3K3s3jWBiYk8FZEA$ >>>> >>> _______________________________________________ >>> Wien mailing list >>> [email protected] >>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >>> <https://urldefense.com/v3/__http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien__;!!Dq0X2DkFhyF93HkjWTBQKhk!Aiu01CYsxX-RFTblmnYIFxWaDSebRoYf8Zf5zW4wj-wJ01RWFttMHgnW4ZPulW1pW2XcjA$> >>> SEARCH the MAILING-LIST at: >>> http://www.mail-archive.com/[email protected]/index.html >>> <https://urldefense.com/v3/__http://www.mail-archive.com/[email protected]/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Aiu01CYsxX-RFTblmnYIFxWaDSebRoYf8Zf5zW4wj-wJ01RWFttMHgnW4ZPulW2mwzz9EQ$> >>> >> _______________________________________________ >> Wien mailing list >> [email protected] >> >> https://urldefense.com/v3/__http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien__;!!Dq0X2DkFhyF93HkjWTBQKhk!Aiu01CYsxX-RFTblmnYIFxWaDSebRoYf8Zf5zW4wj-wJ01RWFttMHgnW4ZPulW1pW2XcjA$ >> SEARCH the MAILING-LIST at: >> https://urldefense.com/v3/__http://www.mail-archive.com/[email protected]/index.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!Aiu01CYsxX-RFTblmnYIFxWaDSebRoYf8Zf5zW4wj-wJ01RWFttMHgnW4ZPulW2mwzz9EQ$ >> > _______________________________________________ > Wien mailing list > [email protected] > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://www.mail-archive.com/[email protected]/index.html >
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