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<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>
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<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>
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