Hi Vic, I haven't used pp.x for a while for spinpolarized systems so I'm not sure about the state of the code in that regard but I can answer some of your other questions. The plot_num=0 density (aka valence pseudo-density) is built as the sum of the squares of the pseudo-KS states, which have been smoothed near the nuclei. The valence pseudo-density integrates to the number of valence electrons in your calculation. Bader integration relies on having maxima at the nuclei but the smoothing may cause some of them to be missing. Therefore, it is a poor idea to use this density to partition the crystal space into atomic regions.
In PAW, you can reconstruct the "correct" (i.e. not smoothed) valence charge density. This is plot_num=17. If, on top of that, you add the core density, then you have the all-electron charge density (plot_num=21). These two densities are poorly represented by a uniform grid and they do not integrate to an integer number of electrons. But they are what you need to use to find the atomic basins. Once the basins are found, you integrate the valence pseudo-density (plot_num=0) inside them to find the atomic charges. You can use plot_num=0 to find the basins. If you have enough valence electrons and little charge transfer, you may very well have maxima on top of all atoms. However, the results will be off. Also, regardless of how you partition the system into atoms, the sum of all atomic populations will trivially give the number of valence electrons always, so that's not a good measure of quality. I have some notes on the atomic integration topic here: https://aoterodelaroza.github.io/critic2/examples/example_11_01_simple-integration/ using the critic2 program but I believe they should apply to Henkelman's code as well. As for why symmetry-equivalent atoms come out with different atomic populations: because the uniform grid on which the density is written doesn't have the same symmetry as the crystal. However, in the limit of an infinitely fine grid the atomic populations should converge to the same value. You may want to try the Yu and Trinkle method implemented in critic2, which assigns fractional weights to grid points and is in general a little more accurate than Henkelman's, but I believe a finer grid is the ultimate solution. Best, Alberto -- Dr. Alberto Otero de la Roza Ramón y Cajal fellow, Department of Physical and Analytical Chemistry, University of Oviedo _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users