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<div>Dear everyone,</div><div><br></div><div>I have a naive question about the number of k points in PHonon calculations.</div><div><span style="line-height: 1.5;">I have a magnetic system (nspin=2) under calculation for the phonon DOS. The crystal structure is bcc-like with space group number of 229 (a supercell of bcc lattice, which contains a single impurity atom) . I observe that in the output of ph.x the number of k points is doubled, compared with what was given by pw.x. I also observe that the number of k points remain the same with both codes for non-magnetic system. Does that mean magnetic systems involve some symmetry operations which must be discarded during the DFPT calculation? And does that mean the ratio of the numbers of k points must be 2:1 (N_ph : N_pw) ?</span></div><div><br></div><div>(I'm using 5.4.0, if this matters)</div><div><br></div><div>Also another naive question. How should I estimate the time cost of PHonon calculations?</div><div>In the guide, it is said that "<span style="line-height: 1.5;">each of the 3</span><i style="line-height: 1.5;">N</i><sub>at</sub><span style="line-height: 1.5;"> modes requires a time of the same order of magnitude of self-consistent calculation in the same system</span><span style="line-height: 1.5;">". From the source code, it appears a nscf calculation usually is necessary. So would the following formulation be correct,</span></div><div>For each q point : t_total = t_nscf + sum_over_representations (Num_modes_each_representation * t_scf)</div><div><span style="line-height: 1.5;"><br></span></div><div><br></div><div>Many thanks for your explanation</div><div><br></div><div>Yi Wang</div><div>----------------------------------------------------------</div><div>Nanjing University of Science and Technology, China</div><style type="text/css">
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