Dear users,
I am running a simple 2-atomic non-magnetic (NM) bcc Cr system (see
below for the input file) with v.4.2.1 and I keep getting an error
message regarding a negative dr2:
from mix_rho : error # 1
negative dr2
This error occurs for values close to as well as away from the
estimated equilibrium volume. What is the possible the origins of this
error and how may I eliminate it?
I have tried to change the mixing_beta in the range 0.1 to 0.8, as
well as changing the mixing mode to 'TF'. I have also tried to set
nspin = 2 with a zero start magnetisation since an anti-ferromagnetic
(AFM) start configuration does not give rise to the problem (but
yields the AFM solution instead of the NM one). However. this also
gives the error. Finally, I tested to use ibrav = 3 and with only one
atom in the cell, but I still get the above error.
What I have noticed is that in the AFM case I get a couple of very
flat bands in the bandstructure just above the Fermi level. If I
change to a USPP potential or an alternative PAW potential these bands
disappear, and the above error does not occur. Can the potential I use
in the present case be the source to the error, and if yes, what is
the reason behind it?
I would appreciate any help or suggestions.
Dan
%-------------------------------------
&CONTROL
calculation = 'scf',
restart_mode = 'from_scratch',
prefix = 'Cr',
tstress = .true.,
tprnfor = .true.,
pseudo_dir =
'/home/forsdan/PROGRAMS/QUANTUM_ESPRESSO/espresso-4.2.1_intel/pseudo/',
outdir = '/home/forsdan/FeCr_PROJECT/TEMP_PAW/'
/
&SYSTEM
ibrav = 1, celldm(1) = 5.378798, nat = 2, ntyp = 1,
ecutwfc = 40.0, ecutrho = 180.0, nbnd = 14
occupations = 'smearing',
smearing = 'mp', degauss = 0.022,
nspin = 1,
/
&ELECTRONS
electron_maxstep = 100,
conv_thr = 1.0d-8,
diagonalization = 'cg',
mixing_mode = 'plain',
mixing_beta = 0.3
/
ATOMIC_SPECIES
Cr 51.996 Cr.pbe-paw_kj_6.UPF
ATOMIC_POSITIONS {crystal}
Cr 0.00 0.00 0.00
Cr 0.50 0.50 0.50
K_POINTS {automatic}
12 12 12 0 0 0
%-------------------------------------
