On Wed, Dec 23, 2020 at 1:46 PM mkondrin <[email protected]> wrote:
&SYSTEM > ibrav = 0 > A = 5.658 > A is the experimental lattice parameter and would be fine for ibrav=2 (fcc), but then you set your lattice vectors: CELL_PARAMETERS (alat= 10.69207046) > -0.510237966 0.000000000 0.510237966 > -0.000000000 0.510237966 0.510237966 > -0.510237966 0.510237966 0.000000000 > to a larger cell (they are in "alat" unit, that is, the value specified as "A" or "celldm(1)", NOT the value in the card). With ibrav=2 you get something like 290 cm^-1. Note that the phonons are typically computed at the theoretical equilibrium lattice parameter, that in LDA is typically smaller than the experimental, leading to higher frequencies. Also note that the convergence threshold conv_thr=1.e-5 in the scf calculation is too large: reduce it to at least 1.0e-8 (it costs close to nothing with respect to the phonon calculation) Paolo -- Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
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