Dear Users I am trying to understand how quantum espresso (pw) is symmetrizing the charge density rhog in reciprocal space. My understanding is that for a nonmagnetic symmorphic crystal structure all components of rhog in a star should be equal [Streitwolf, Group Theory in Physics, Eq. (6.8)].
For systems with zincblende structure this is, indeed, what I get. However, for systems with wurtzite structure half of the components in some stars have opposite signs. More specifically, I have checked that sym_rho_init_shells identifies the stars as expected. However, sym_rho_serial then gives opposite signs for half of the components in some stars. The code in sym_rho_init_shells is quite straightforward, using integer arithmetic for the transformations of the reciprocal lattice vectors. This code is doing what I expect, and it gives the results I expect. However, I have not yet got the same level of understanding for sym_rho_serial. The latter routine is doing something more complicated, implementing the transformations of the reciprocal lattice vectors via floating point arithmetic where I do not understand the reason for this different approach. I can merely say that I have instrumented sym_rho_serial to write out the density after symmetrization and I do not get what I expect as described above. [For example, for the job attached below, the components 12,14,16,18,20,22 and 13,15,17,19,21,23 of rhog form two stars (according to sym_rho_init_shells), but the corresponding values of rhog in each of these stars are not equal.] Am I missing something? Any help is appreciated. My input file for pw.x is attached. I am using version 7.5. Roland Winkler &CONTROL calculation='scf' verbosity='high' prefix='zns' ! Output files are named according to prefix / &SYSTEM space_group=186 ! Space group number a=3.811 ! Lattice parameter a in angstroms c=6.234 ! Lattice parameter c in angstroms nat=2 ! Number of atoms in the asymmetric unit ntyp=2 ! Number of different atom types. Here, Zn and S. ecutwfc=40 ! Kinetic energy cutoff for wavefunctions (Ry) ecutrho=200 ! Kinetic energy cutoff for charge density and potential (Ry) / &ELECTRONS / &IONS / &CELL / ATOMIC_SPECIES Zn 65.38 zn_pbe_v1.uspp.F.UPF S 32.065 s_pbe_v1.4.uspp.F.UPF ATOMIC_POSITIONS crystal_sg Zn 1/3 2/3 0.00000 S 1/3 2/3 0.38500 K_POINTS automatic 2 2 2 0 0 0 _______________________________________________________________________________ The Quantum ESPRESSO Foundation stands in solidarity with all civilians worldwide who are victims of terrorism, military aggression, and indiscriminate warfare. -------------------------------------------------------------------------------- Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
