<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>Please read the literature about hybrid functionals in plane waves; understand why the computational time is, not unexpectedly, huge and start think about it.</div><div id="AppleMailSignature"> If you come up with some smart idea on how to reduce the computational time without compromising accuracy (as for the ACE transformation recently proposed by Lin Lin and implemented in the latest QE version) let us know<br>Best,<br>stefano <div>(sent from my phone)</div></div><div><br>On 09 Sep 2016, at 09:30, Daniel Stoeffler <<a href="mailto:daniel.stoeffler@ipcms.unistra.fr">daniel.stoeffler@ipcms.unistra.fr</a>> wrote:<br><br></div><blockquote type="cite"><div>
<p> </p>
<p>Hello,</p>
<p>As a new QE user, I do some tests with the HSE Functional for BCC ferromagnetic Fe with a cell containing 2 atoms (because a want to go to CoFe after that).</p>
<p>My input file is :</p>
<p> &control<br> title='Fe CC HSE',<br> calculation = 'scf',<br> prefix = 'Fe_CC_HSE',<br> pseudo_dir='./',<br> verbosity = 'high'<br> /<br> &system<br> ibrav = 6, <br> celldm(1) = 5.45, <br> celldm(3) = 1.0,<br> nat = 2, <br> ntyp = 1,<br> nspin = 2,<br> occupations='smearing', smearing='gauss', degauss=0.01,<br> starting_magnetization(1) = 1.0,<br> ecutwfc = 33,<br> input_dft='HSE', <br> report = 5<br> /<br> &electrons<br> mixing_beta = 0.7<br> /<br><br>ATOMIC_SPECIES<br> Fe 55.845 Fe.pbe-sp-van.UPF<br> <br>ATOMIC_POSITIONS (crystal)<br>Fe 0.000 0.000 0.000<br>Fe 0.500 0.500 0.500<br><br>K_POINTS (automatic)<br> 7 7 7 0 0 0<br><br></p>
<p>Surprisingly, the computation time is huge as writen into the output file :</p>
<p>===============================</p>
<p> iteration # 9 ecut= 33.00 Ry beta=0.70<br> Davidson diagonalization with overlap<br> ethr = 5.49E-08, avg # of iterations = 2.3<br> <br> Magnetic moment per site:<br> atom: 1 charge: 14.4350 magn: 2.6346 constr: 0.0000<br> atom: 2 charge: 14.4351 magn: 2.6343 constr: 0.0000<br><br> total cpu time spent up to now is 7.2 secs<br><br> End of self-consistent calculation<br><br></p>
<p> convergence has been achieved in 9 iterations<br><br> EXX: now go back to refine exchange calculation<br><br> total cpu time spent up to now is 4239.4 secs<br><br> Self-consistent Calculation<br><br> iteration # 1 ecut= 33.00 Ry beta=0.70<br> Davidson diagonalization with overlap<br> ethr = 5.49E-08, avg # of iterations = 4.9<br><br> total cpu time spent up to now is 52490.2 secs<br><br> iteration # 2 ecut= 33.00 Ry beta=0.70<br> Davidson diagonalization with overlap<br><br></p>
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<p>So, the calculation takes 7 seconds for converging with PBE, 1h10min for calculating the EXX term and 14h35min for the first HSE iteration. Is this correct ? And if so, please, could you try to explain me how to reduce the computation time. Thanks in advance.</p>
<p>Best wishes,</p>
<p>Daniel</p>
<p> </p>
<div> </div>
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