[Pw_forum] problem on phonon
On Sat, May 28, 2011 at 10:52 PM, bhabya sahoo wrote: > sir > i am using quantum espresso 4.3 version > i want to study the phase transition of yitrium nitride(yn) > first by doing scf calculation at 0k > i found a phase transition of B1 to B2 transition at 137 gpa for this i > used a 14*14*14 kpoints mesh and convergence achived for scf is 10^-9 > i used GGA psudo potentials of pbe type avalable in code of espresso > website for y and n > but when i did the calculation for phonon dispersion > B2 stucter instablity (negative frequency ) in phonon spectrum continues > upto 500 gpa why ? > for this i used 4*4*4* mesh q points for dyanamical matrices i have > incresed further but nothing results > > On Sat, May 28, 2011 at 9:36 PM, Stefano de Gironcoli sissa.it>wrote: > >> Dear Bhabya Sahoo, >> >>your very stingy use of punctuation make quite difficult (at least for >> me) to follow your request... >>Take your time and try to make you clear providing more detailed >> information about your system, what is your aim, what is the problem, what >> are the tests you have done. >>No one is going to spend more time in thinking about your problem than >> you do in explaining it. >> >>Please provide your affiliation. >> >>stefano >> - >> Stefano de Gironcoli, SISSA and DEMOCRITOS >> >> >> On 05/28/2011 05:46 PM, bhabya sahoo wrote: >> >> i am using quantum espresso static calculation obeys thermdyanamic stability >> transition from B1 to B2 transition at 138 gpa so ihave used 24 24 24 >> kpoint grid for phonon in B2 phase is calculated 4 4 4 grid by linear >> response calculation but why the instability (negative frequency in phonon ) >> upto 450 gpa i have used pbe psudo potentials also the lattice constant is >> exact for experimental data >> can metastability have negative frequency so why this occures >> optimisation is ok >> other problem why free energy is not coming for unstable phase for qha code >> in quantum espresso >> replay immidiate if u have solution >> On Sat, May 28, 2011 at 5:38 PM, bhabya sahoo >> wrote: >> >> >> sir >> i used to calculate the phonon calculation on a 4*4*4 grid in cscl phase >> but the unstability persists upto 500 gpa >> but it is the thermodyanamic stability after 140 gpa kpoints 24*24*24 >> what may be reseon i donot know >> please help me >> >> >> >> ___ >> Pw_forum mailing list >> Pw_forum at pwscf.orghttp://www.democritos.it/mailman/listinfo/pw_forum >> >> >> >> ___ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://www.democritos.it/mailman/listinfo/pw_forum >> >> > -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110529/4ca703fd/attachment.htm
[Pw_forum] problem on phonon
On Sat, May 28, 2011 at 5:38 PM, bhabya sahoo wrote: > sir > i used to calculate the phonon calculation on a 4*4*4 grid in cscl phase > but the unstability persists upto 500 gpa > but it is the thermodyanamic stability after 140 gpa kpoints 24*24*24 > what may be reseon i donot know > please help me > -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110529/ba5d2bd1/attachment.htm
[Pw_forum] problem on phonon
sir i am using quantum espresso 4.3 version i want to study the phase transition of yitrium nitride(yn) first by doing scf calculation at 0k i found a phase transition of B1 to B2 transition at 137 gpa for this i used a 14*14*14 kpoints mesh and convergence achived for scf is 10^-9 i used GGA psudo potentials of pbe type avalable in code of espresso website for y and n but when i did the calculation for phonon dispersion B2 stucter instablity (negative frequency ) in phonon spectrum continues upto 500 gpa why ? for this i used 4*4*4* mesh q points for dyanamical matrices i have incresed further but nothing results On Sat, May 28, 2011 at 9:36 PM, Stefano de Gironcoli wrote: > Dear Bhabya Sahoo, > >your very stingy use of punctuation make quite difficult (at least for > me) to follow your request... >Take your time and try to make you clear providing more detailed > information about your system, what is your aim, what is the problem, what > are the tests you have done. >No one is going to spend more time in thinking about your problem than > you do in explaining it. > >Please provide your affiliation. > >stefano > - > Stefano de Gironcoli, SISSA and DEMOCRITOS > > > On 05/28/2011 05:46 PM, bhabya sahoo wrote: > > i am using quantum espresso static calculation obeys thermdyanamic stability > transition from B1 to B2 transition at 138 gpa so ihave used 24 24 24 > kpoint grid for phonon in B2 phase is calculated 4 4 4 grid by linear > response calculation but why the instability (negative frequency in phonon ) > upto 450 gpa i have used pbe psudo potentials also the lattice constant is > exact for experimental data > can metastability have negative frequency so why this occures > optimisation is ok > other problem why free energy is not coming for unstable phase for qha code > in quantum espresso > replay immidiate if u have solution > On Sat, May 28, 2011 at 5:38 PM, bhabya sahoo > wrote: > > > sir > i used to calculate the phonon calculation on a 4*4*4 grid in cscl phase > but the unstability persists upto 500 gpa > but it is the thermodyanamic stability after 140 gpa kpoints 24*24*24 > what may be reseon i donot know > please help me > > > > ___ > Pw_forum mailing list > Pw_forum at pwscf.orghttp://www.democritos.it/mailman/listinfo/pw_forum > > > > ___ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110528/da419bf8/attachment.htm
[Pw_forum] problem on phonon
i am using quantum espresso static calculation obeys thermdyanamic stability transition from B1 to B2 transition at 138 gpa so ihave used 24 24 24 kpoint grid for phonon in B2 phase is calculated 4 4 4 grid by linear response calculation but why the instability (negative frequency in phonon ) upto 450 gpa i have used pbe psudo potentials also the lattice constant is exact for experimental data can metastability have negative frequency so why this occures optimisation is ok other problem why free energy is not coming for unstable phase for qha code in quantum espresso replay immidiate if u have solution On Sat, May 28, 2011 at 5:38 PM, bhabya sahoo wrote: > sir > i used to calculate the phonon calculation on a 4*4*4 grid in cscl phase > but the unstability persists upto 500 gpa > but it is the thermodyanamic stability after 140 gpa kpoints 24*24*24 > what may be reseon i donot know > please help me > -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110528/54fd37f5/attachment-0001.htm
[Pw_forum] problem on phonon
Dear Bhabya Sahoo, your very stingy use of punctuation make quite difficult (at least for me) to follow your request... Take your time and try to make you clear providing more detailed information about your system, what is your aim, what is the problem, what are the tests you have done. No one is going to spend more time in thinking about your problem than you do in explaining it. Please provide your affiliation. stefano - Stefano de Gironcoli, SISSA and DEMOCRITOS On 05/28/2011 05:46 PM, bhabya sahoo wrote: > i am using quantum espresso static calculation obeys thermdyanamic stability > transition from B1 to B2 transition at 138 gpa so ihave used 24 24 24 > kpoint grid for phonon in B2 phase is calculated 4 4 4 grid by linear > response calculation but why the instability (negative frequency in phonon ) > upto 450 gpa i have used pbe psudo potentials also the lattice constant is > exact for experimental data > can metastability have negative frequency so why this occures > optimisation is ok > other problem why free energy is not coming for unstable phase for qha code > in quantum espresso > replay immidiate if u have solution > On Sat, May 28, 2011 at 5:38 PM, bhabya sahoo wrote: > >> sir >> i used to calculate the phonon calculation on a 4*4*4 grid in cscl phase >> but the unstability persists upto 500 gpa >> but it is the thermodyanamic stability after 140 gpa kpoints 24*24*24 >> what may be reseon i donot know >> please help me >> > > > ___ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110528/a0b31bdf/attachment.htm
[Pw_forum] problem on phonon
Dear Sahoo, Without knowing your input file, how one can judge. Please provide your input file. Further, not fully optimization may be one reason. Best SKG Dept. of Phys. Bhavnagar University Gujarat On Sat, May 28, 2011 at 5:38 PM, bhabya sahoo wrote: > sir > i used to calculate the phonon calculation on a 4*4*4 grid in cscl phase > but the unstability persists upto 500 gpa > but it is the thermodyanamic stability after 140 gpa kpoints 24*24*24 > what may be reseon i donot know > please help me > > ___ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110528/947b2660/attachment.htm
[Pw_forum] problem on phonon
sir i used to calculate the phonon calculation on a 4*4*4 grid in cscl phase but the unstability persists upto 500 gpa but it is the thermodyanamic stability after 140 gpa kpoints 24*24*24 what may be reseon i donot know please help me -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110528/d72e13ef/attachment.htm
