Hello The stars of G vectors depend on the group with all the symmetries of the lattice. The charge symmetrization is done using the symmetries of the crystal structure, i.e. the subgroup of the lattice rotations that do not alter the atomic structure. If the group and subgroup don' t coincide the charge fourier components do not necessarily coincide over the whole shells of G vectors. The symmetrization of rho_G is a bit more complicated because for each rotation S belonging to the crystal group you need to find the vector G' which is brought to G by S. Pietro
Il 12 mar 2026 7:21 PM, Roland Winkler <[email protected]> ha scritto: 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<http://www.max-centre.eu>) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________________________________________ 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
