The stress converges _very_ slowly with cutoff. The ultimate test for stress is to compare it with the numerical derivatives of the energy, computed at a _fixed_ number of plane waves. This has been done more than once and I am quite sure that the stress is correctly computed. There are still some problems in variable-cell calculations, though, of unclear origin: https://gitlab.com/QEF/q-e/-/issues/204.
Paolo On Thu, Oct 14, 2021 at 1:17 PM Audrius Alkauskas <audrius.alkaus...@ftmc.lt> wrote: > Dear all, > > We have started testing the Quantum Espresso implementation of screened > Fock exchange (HSE functional), benchmarking against VASP results (the > input file below). > > As a test case, we took simple bulk diamond. If we calculate the energy > as a function of the lattice constant, the resulting equilibrium lattice > parameter (3.555 A) and bulk modulus are very similar to the results > from VASP, which is nice. However, the calculated stress for the > equilibrium lattice parameter is still large (~30 kBar). The stress is > linear as a function of the lattice constant and is ~0 for the lattice > constant 3.585 A, yielding an offset of about 0.03 A with respect to > what I assume is the "correct" HSE value. The value of 3.585 A is much > closer to the PBE result. Are there still some issues when calculating > stresses with hybrids or we do something wrong? Energies seem OK, > stresses not (the error is not huge, but still...) > > If anybody has any insights, I would be happy to get receive them. > > Best, > Audrius > > *** > Input > *** > > &CONTROL > calculation = 'scf' > title = 'carbon-cubic-hse-3.556' > verbosity = 'high' > nstep = 100 > tstress = .true. > tprnfor = .true. > outdir = '/home/vytautas/HSE/C/relax/3.556' > etot_conv_thr = 1e-06 > forc_conv_thr = 1e-05 > pseudo_dir = '.' > / > &SYSTEM > ibrav = 1 > celldm = 6.719866103476117 > nat = 8 > ntyp = 1 > nbnd = 24 > ecutwfc = 100 > ecutrho = 400 > ecutfock = 400 > input_dft = 'hse' > exxdiv_treatment = 'gygi-baldereschi' > x_gamma_extrapolation = .true. > nqx1 = 4 > nqx2 = 4 > nqx3 = 4 > celldm(1) = 6.719866131544066 > / > &ELECTRONS > electron_maxstep = 300 > conv_thr = 1e-08 > / > &IONS > / > &CELL > / > > ATOMIC_SPECIES > C 12.011 C.upf > > K_POINTS automatic > 4 4 4 0 0 0 > > ATOMIC_POSITIONS angstrom > C 0.0000000000 0.0000000000 0.0000000000 > C 1.7780000000 1.7780000000 0.0000000000 > C 0.8890000000 0.8890000000 0.8890000000 > C 2.6670000000 2.6670000000 0.8890000000 > C 0.0000000000 1.7780000000 1.7780000000 > C 1.7780000000 0.0000000000 1.7780000000 > C 0.8890000000 2.6670000000 2.6670000000 > C 2.6670000000 0.8890000000 2.6670000000 > > > > -- > Audrius Alkauskas > Center for Physical Sciences and Technology (FTMC) > Vilnius, Lithuania > > email: audrius.alkaus...@ftmc.lt > phone: +370 612 22281 > www.puntukas.com / www.ftmc.lt > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users -- Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, Univ. Udine, via delle Scienze 206, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
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