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Hi! <BR>
<BR>
Regarding k-points: The program will use symmetry to reduce the amount of used k-points as much as possible, i.e. those found in the irreducible BZ. Those might just be 60 in your case. <BR>
<BR>
Regarding phonons: You need to change occupation from smearing. That one is appropriate for metals but not for insulators. Use 'fixed' instead. Check the documentation for details. <BR>
<BR>
Best,<BR>
Adam Jacobsson<BR><BR><BR>
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Date: Mon, 22 Dec 2008 16:05:50 +0530<BR>From: lataprem29@gmail.com<BR>To: pw_forum@pwscf.org<BR>Subject: [Pw_forum] about phonon calculation<BR><BR>Dear Pwscf users,<BR>Here I am sending you the input file of Li2S (large band gap semi-conductor) for scf and phonon calculations. I have some queries regarding this<BR><BR>1. For electronic calculation i am using 8x8x8 k-points which results in only 60 points. Is it enough to do correct electronic calculations?<BR>With these 60 points only, I calculated the bulk mobulus and the equilibrium lattice constants, which matches well with the experiment and other theoritical results.<BR><BR>2. For phonon calculation, I didnt get the LO-TO splitting. Can you please tell me what more parameters i will use to get the splitting. <BR>I set epsil .true., but it gives the error <BR><BR> from phq_readin : error # 1<BR> no elec. field with metals<BR><BR>Any suggestion is highly apperciable <BR><BR><A href="http://li2s.scf.in/">li2s.scf.in</A><BR><BR>&CONTROL<BR> calculation = 'scf' ,<BR> restart_mode = 'from_scratch' ,<BR> outdir = './OUT',<BR> pseudo_dir = '/root/bipul/espresso-4.0.1/pseudo/Li2S',<BR> prefix = 'Li2S',<BR> etot_conv_thr = 1.0d-5 ,<BR> forc_conv_thr = 1.0d-4 ,<BR> tstress = .true. ,<BR> tprnfor = .true. ,<BR> dt = 80<BR> /<BR> &SYSTEM<BR> ibrav = 2,<BR> celldm(1) = 10.72700,<BR> nat = 3,<BR> ntyp = 2 ,<BR> ecutwfc = 32,<BR> ecutrho = 600,<BR> occupations = 'smearing' ,<BR> smearing = 'methfessel-paxton',<BR> degauss = 0.01<BR> /<BR> &ELECTRONS<BR> mixing_beta = 0.5 ,<BR> conv_thr = 1.0d-8<BR> diagonalization = 'david' ,<BR> /<BR> &IONS<BR> /<BR>ATOMIC_SPECIES<BR> S 32.066 S.pw91-van_ak.UPF<BR> Li 6.914 Li.pw91-s-van_ak.UPF<BR>ATOMIC_POSITIONS (crystal)<BR>S 0.0 0.0 0.0<BR>Li 0.25 0.25 0.25<BR>Li 0.75 0.75 0.75<BR>K_POINTS automatic<BR> 8 8 8 1 1 1<BR><BR><A href="http://li2s.ph.in/">li2s.ph.in</A><BR><BR>phonons of Li2S<BR> &inputph<BR> ! recover =.true.,<BR> tr2_ph=1.0d-12,<BR> alpha_mix(1)=0.6,<BR> prefix='Li2S',<BR> ! fildvscf='li2sdv',<BR> amass(1)=32.066,<BR> amass(2)=6.941,<BR> outdir='./OUT',<BR> fildyn='li2s.dyn',<BR> ! elph=.true.,<BR> ! trans=.true.,<BR> ldisp=.true.<BR> nq1=4, nq2=4, nq3=4<BR> /<BR><BR clear=all><BR>-- <BR>Premlata Pandit<BR>Ph.d. student,<BR>Barkatullah university,<BR>Bhopal 462026,<BR>MP, India <BR><BR><br /><hr />Lägg till karta och vägbeskrivning för din fest. <a href='http://www.microsoft.com/windows/windowslive/events.aspx' target='_new'>Visa vägen! </a></body>
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