[QE-users] large negative rho

[K. Doblhoff-Dier]

Dear QE users and developers,

I performed DFT calculations using the grvb-1.4 uspp for Pt (just a 
single atom in a cell) and I get rather large negative values for rho 
even after scf convergence:

-----snippet of the pwscf log 
file-----------------------------------------------------

      negative rho (up, down):  1.759E-01 0.000E+00
      total cpu time spent up to now is       41.4 secs
      End of self-consistent calculation
      Number of k-points >= 100: set verbosity='high' to print the bands.
      the Fermi energy is    22.2850 ev
!    total energy              =    -210.69743345 Ry

------end of 
snippet---------------------------------------------------------------------

Usually, I would have thought that this is a sign of a too low ecutwfc 
(or actually ecutrho). But, while very similar results were obtained for 
ecutwfc=35Ry and ecutrho=280Ry, the above results were obtained for 
ecutwfc=100Ry and ecutrho=1000Ry, which should be crazily large for the 
PP in question.

I guess, one might say that -0.17e can be safely ignored (see the pwscf 
faq), and the lattice constant and bulk modulus are indeed totally 
reasonable. However, the error scales with number of atoms, so once I go 
to a Pt slab, I get negative charges around -3e and I am hesitant to 
accept that without thinking twice.

A very similar question has been posed before 
(https://www.mail-archive.com/users@lists.quantum-espresso.org/msg18381.html), 
but has not been answered.

Any hints?

Thanks in advance

Katharina Doblhoff-Dier