[Pw_forum] cell optimization

[hania djani-ait aissa]

Dear Baroni,
thank you, but it seems i am not using US pps. However, I will increase ecutrho and see.
thanks again
hania


From: baroni at sissa.itTo: pw_forum at pwscf.orgDate: Sun, 22 Jun 2008 14:32:02 +0200Subject: Re: [Pw_forum] cell optimizationI may be wrong, but your problem could be due to subtelties of the US PP formalism. Using US PPs, I am afraid that PW calculations are variational with respect to PW expansion coefficients only when the augmentation charge is at convergence. Convergence with respect to the augmentation charge usually is a rather delicate issue. For sure, the cutoff for the charge-density distribution (ecutrho) should be taken larger (sometimes much larger) than the default value for norm-conserving PPs (4 x ecutwfc). In yor calculation, you seem to use just this value, which may turn out to be inadequate. Have you tried to test the convergence of your calcs wrt echutrho (keeping ecutwfc fixed)? SB 


On Jun 22, 2008, at 11:06 AM, hania djani-ait aissa wrote:

Dear Nicola,I have tried startingwfc='random' and it gave me the same energies values as for startingwfc='atomic' with still the same problem of drop and rise of total energy. I also increase Ecutoff to 40Ry, the energies values are actually more accurate but the problem persist. Hania  
 &control    calculation  = 'scf'    restart_mode = 'from_scratch'    pseudo_dir   = '/root/pwscf/pseudo/'    outdir       = '/root/tmp/' / &system    ibrav=7    celldm(1)=7.33, celldm(3)=8.54    nat=19    ntyp=3    ecutwfc=25.0    ecutrho=100.0 / &electrons    conv_thr = 1e-6,    mixing_beta=0.2,
    startingwfc=’random’ /ATOMIC_SPECIES  Bi    208.98    Bi.pbe-d-mt.UPF  Ti    47.867    Ti.pbe-sp-van_ak.UPF  O     15.9994   O.pbe-van_ak.UPFATOMIC_POSITIONS  Bi 0.00000000 0.00000000 0.5713404 Bi 0.00000000 0.00000000 7.9816596 Bi 0.00000000 0.00000000 1.8072489 Bi 0.00000000 0.00000000 6.7457511 Ti 0.00000000 0.00000000 3.1757289 Ti 0.00000000 0.00000000 5.3772711 Ti 0.00000000 0.00000000 4.2765000 O  0.50000000 0.00000000 0.0000 O  0.00000000 0.50000000 0.0000 O  0.50000000 0.00000000 2.13825 O  0.50000000 0.00000000 6.41475 O  0.00000000 0.00000000 3.771873 O  0.00000000 0.00000000 4.781127 O  0.00000000 0.00000000 2.7241305 O  0.00000000 0.00000000 5.8288695 O  0.50000000 0.00000000 1.0049775 O  0.50000000 0.00000000 7.5480225 O  0.00000000 0.50000000 1.0049775 O  0.00000000 0.50000000 7.5480225K_POINTS {automatic}  4 4 4 1 1 1  

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Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
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