[Pw_forum] Charge and spin densities on radial grid given by PAW calculations

[Lorenzo Paulatto]

On Mon, 11 Jan 2010 05:20:52 +0100, Jones Tsz-Kai Wan  
<jwan at phy.cuhk.edu.hk> wrote:

> Dear PWSCF users,
>
> I am working on hyperfine tensor and I need very precise description
> of charge and spin densities using PAW method. I suppose such
> densities are first calculated using radial grid in the code. However,
> the charge and spin densities are only given on the regular grid, but
> not on the radial grid. Does anyone know how I can obtain the
> charge/spin density on radial grid?


Dear Jones,
the PAW method does actually compute the one-center charges on radial  
grids, but our implementation does not store it longer than necessary;  
i.e. it is discarded right after computing the one-center contributions to  
total energy. Nevertheless, you can alway reconstruct it from the "becsum"  
terms:
  becsum_ij = \sum_n f_n <psi_n|beta_i><beta_j|psi_n> .
They are always stored and saved to file at the end of calculation.

You can find a prototype function that computes the all-electron valence  
charge density on the real-space grid in recent enough (maybe only CVS)  
versions of QE. Have a look at file PP/paw_postproc.f90 and at how it's  
called in PP/punchplot.f90

best regards


-- 
Lorenzo Paulatto

*** Note: my affiliation has changed! please send future
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post-doc @ IMPMC/UPMC - Université Paris 6
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