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Hi VASP admin and users,

I'm interested in obtaining the superposition of atomic charge density that is used to initialize the SCF calculation. Can you point me the right way to obtain this information?

What I've tried is to (1) first set IALGO = -1; this makes VASP not do any self-consistent steps, and (2) set LAECHG = True; this outputs some additional density grids, including the superposition of atomic densities. It will also output AECCAR0 and AECCAR1 and perhaps AECCAR1 is the superposition of atomic charge density?

Thanks,
Lin

It depends a bit what you need. If all you want is the superposition of the valence charge density on the FFT grid, you can use the file AECCAR1. If you want the exact density that VASP uses at the start of the calculation, you would need to modify the code to print the density to file after the initialization. The initial charge density is different from the atomic density e.g. in the case of magnetism. Finally, if you want the all-electron density, you would need to add the contribution of the core electrons in AECCAR0.