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--></style></head><body lang=EN-US link=blue vlink="#954F72"><div class=WordSection1><p class=MsoNormal>Dear all QE users,</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am calculating phonon dispersion using two modes of PH module of quantum espresso. One mode is to split total calculation into calculations of each irreducible q point (SPLIT), while the other is the GRID calculation as the demonstrated in the GRID_example, which is to take all the irreducible representations into consideration. However, the output files shows different information when I use these two method to calculate phonon frequency with the same structure and scf input. The main difference is that in the output of GRID method there is a warning shown below:</p><p class=MsoNormal>##########################################################</p><p class=MsoNormal> Starting wfc are 267 atomic wfcs</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Possibly too few bands at point 1 -0.12500 0.12500 0.12500</p><p class=MsoNormal>Possibly too few bands at point 2 0.37500 -0.37500 0.62500</p><p class=MsoNormal>Possibly too few bands at point 3 -0.37500 0.37500 -0.12500</p><p class=MsoNormal>Possibly too few bands at point 4 0.12500 -0.12500 0.37500</p><p class=MsoNormal>…</p><p class=MsoNormal>…</p><p class=MsoNormal>…</p><p class=MsoNormal>Possibly too few bands at point 87 -1.12500 -0.37500 -0.37500</p><p class=MsoNormal>Possibly too few bands at point 88 -0.62500 -0.87500 0.12500</p><p class=MsoNormal>##########################################################</p><p class=MsoNormal>While there is no such information in the output file of SPLIT method. </p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The input of GRID method for each irreducible representation is shown below </p><p class=MsoNormal>##########################################################</p><p class=MsoNormal>Phonon of K3C60</p><p class=MsoNormal> &inputph</p><p class=MsoNormal> tr2_ph=1.0d-17,</p><p class=MsoNormal> prefix='K3C60',</p><p class=MsoNormal> ldisp=.true.</p><p class=MsoNormal> nq1=2, nq2=2, nq3=2</p><p class=MsoNormal> start_q=2</p><p class=MsoNormal> last_q=2</p><p class=MsoNormal> start_irr=’irr_num’,</p><p class=MsoNormal> last_irr=’irr_num’,</p><p class=MsoNormal> amass(1)=12</p><p class=MsoNormal> amass(2)=39.1</p><p class=MsoNormal> outdir='./',</p><p class=MsoNormal> fildyn='K3C60.dynG',</p><p class=MsoNormal> reduce_io = .true.</p><p class=MsoNormal> /</p><p class=MsoNormal>##########################################################<o:p></o:p></p><p class=MsoNormal>And the input of GRID method after collecting all the information of each irreducible representation is </p><p class=MsoNormal>##########################################################</p><p class=MsoNormal>Phonon of K3<o:p></o:p></p><p class=MsoNormal> &inputph<o:p></o:p></p><p class=MsoNormal> tr2_ph=1.0d-17,<o:p></o:p></p><p class=MsoNormal> prefix='K3C60',<o:p></o:p></p><p class=MsoNormal> ldisp=.true.<o:p></o:p></p><p class=MsoNormal> nq1=2, nq2=2, nq3=2<o:p></o:p></p><p class=MsoNormal> recover=.true.,<o:p></o:p></p><p class=MsoNormal> start_q=2<o:p></o:p></p><p class=MsoNormal> last_q=2<o:p></o:p></p><p class=MsoNormal> amass(1)=12<o:p></o:p></p><p class=MsoNormal> amass(2)=39.1<o:p></o:p></p><p class=MsoNormal> outdir='./',<o:p></o:p></p><p class=MsoNormal> fildyn='K3C60.dynG',<o:p></o:p></p><p class=MsoNormal> reduce_io = .true.<o:p></o:p></p><p class=MsoNormal> /<o:p></o:p></p><p class=MsoNormal>##########################################################</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>And the input of SPLIT method is </p><p class=MsoNormal>##########################################################</p><p class=MsoNormal>Phonon of K3C60<o:p></o:p></p><p class=MsoNormal> &inputph<o:p></o:p></p><p class=MsoNormal> tr2_ph=1.0d-17,<o:p></o:p></p><p class=MsoNormal> prefix='K3C60',<o:p></o:p></p><p class=MsoNormal> ldisp=.true.<o:p></o:p></p><p class=MsoNormal> nq1=2, nq2=2, nq3=2<o:p></o:p></p><p class=MsoNormal> start_q=2<o:p></o:p></p><p class=MsoNormal> last_q=2<o:p></o:p></p><p class=MsoNormal> amass(1)=12<o:p></o:p></p><p class=MsoNormal> amass(2)=39.1<o:p></o:p></p><p class=MsoNormal> outdir='./',<o:p></o:p></p><p class=MsoNormal> fildyn='K3C60.dynG',<o:p></o:p></p><p class=MsoNormal> reduce_io = .true.<o:p></o:p></p><p class=MsoNormal> /<o:p></o:p></p><p class=MsoNormal>##########################################################</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Why is there the difference information in the output file for the same structure and scf input? I will appreciate it if anyone could give me any information about that.</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Best regards</p><p class=MsoNormal>Zhishuo Huang</p><p class=MsoNormal><o:p> </o:p></p></div></body></html>