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/[email protected]/msg18381.html),
but has not been answered.
Any hints?
Thanks in advance
Katharina Doblhoff-Dier
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