[Pw_forum] about phonon calculation
adams_mejl at hotmail.com
Mon Dec 22 21:19:22 CET 2008
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.
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.
Date: Mon, 22 Dec 2008 16:05:50 +0530From: lataprem29 at gmail.comTo: pw_forum at pwscf.orgSubject: [Pw_forum] about phonon calculationDear Pwscf users,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 this1. For electronic calculation i am using 8x8x8 k-points which results in only 60 points. Is it enough to do correct electronic calculations?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.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. I set epsil .true., but it gives the error from phq_readin : error # 1 no elec. field with metalsAny suggestion is highly apperciable li2s.scf.in&CONTROL calculation = 'scf' , restart_mode = 'from_scratch' , outdir = './OUT', pseudo_dir = '/root/bipul/espresso-4.0.1/pseudo/Li2S', prefix = 'Li2S', etot_conv_thr = 1.0d-5 , forc_conv_thr = 1.0d-4 , tstress = .true. , tprnfor = .true. , dt = 80 / &SYSTEM ibrav = 2, celldm(1) = 10.72700, nat = 3, ntyp = 2 , ecutwfc = 32, ecutrho = 600, occupations = 'smearing' , smearing = 'methfessel-paxton', degauss = 0.01 / &ELECTRONS mixing_beta = 0.5 , conv_thr = 1.0d-8 diagonalization = 'david' , / &IONS /ATOMIC_SPECIES S 32.066 S.pw91-van_ak.UPF Li 6.914 Li.pw91-s-van_ak.UPFATOMIC_POSITIONS (crystal)S 0.0 0.0 0.0Li 0.25 0.25 0.25Li 0.75 0.75 0.75K_POINTS automatic 8 8 8 1 1 1li2s.ph.inphonons of Li2S &inputph ! recover =.true., tr2_ph=1.0d-12, alpha_mix(1)=0.6, prefix='Li2S', ! fildvscf='li2sdv', amass(1)=32.066, amass(2)=6.941, outdir='./OUT', fildyn='li2s.dyn', ! elph=.true., ! trans=.true., ldisp=.true. nq1=4, nq2=4, nq3=4 /-- Premlata PanditPh.d. student,Barkatullah university,Bhopal 462026,MP, India
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