[Pw_forum] Hubbard U and small degauss ...
Naol Regassa
greatnaol at gmail.com
Sun May 17 12:01:54 CEST 2009
Dear all
I have two questions to ask
a) For the last times I was calculating the effect of Hubbard U on the
system YMnO_3 using QESPRESSO 4.10. I got an insulator band structure
using U = 10.5eV though it is completely metal without U (GGA). When I
got this result I have used small degauss = 0.006. My friend told me
to use degauss = 0.015. Please tell me how possible (correct) is
that? I checked the convergence for degauss but it is increasing near
0.015.
b) Is adding U value more effective for the most stable structure ?
For the unstable states like for my case cubic ferromagnetic phase I
can't see any change?
Here is the input for the 'scf'
&control
calculation = 'scf',
restart_mode = 'from_scratch',
prefix = 'ymo_hcp_ferro'
tstress = .true.,
tprnfor = .true.,
pseudo_dir = '/home/MSC608/Desktop/QESPRESSO_PP',
outdir='/home/MSC608/Thesis/Hexagonal/Ferro-Hex/temp'
/
&system
ibrav = 0,
celldm(1) = 6.7,
nat = 10,
ntyp = 4,
ecutwfc = 32,
ecutrho = 340.0
nspin = 2
starting_magnetization(2) = 0.7,
starting_magnetization(3) = 0.7,
occupations = 'smearing',
smearing = 'marzari-vanderbilt',
degauss = 0.005,
lda_plus_u=.true.,
Hubbard_U(2) = 10.5,
Hubbard_U(3) = 10.5,
/
&electrons
diagonalization = 'david'
startingwfc = 'atomic+random'
mixing_beta = 0.3,
conv_thr = 1.0d-10
/
ATOMIC_SPECIES
Y 88.91 Y.pbe-nsp-van.UPF
Mn1 54.94 Mn.pbe-sp-van_mit.UPF
Mn2 54.94 Mn.pbe-sp-van_mit.UPF
O 15.9994 O.pbe-rrkjus.UPF
CELL_PARAMETERS (alat)
0.985236441 -0.266531554 -0.000316189
-0.266366323 0.985859979 0.000349871
0.000781869 -0.000890980 3.186836665
ATOMIC_POSITIONS (crystal)
Y -0.082663260 -0.082649328 0.000174846
Y -0.082874577 -0.082880779 0.499813069
Mn1 0.205305857 0.560245090 0.249986248
Mn2 0.561457263 0.207812583 0.750012603
O -0.027464907 -0.056329933 0.249979343
O -0.058482388 -0.031289340 0.750035308
O 0.247951998 0.582250730 0.083800805
O 0.582338704 0.248188482 0.916046842
O 0.582135578 0.247948396 0.583964864
O 0.247742343 0.582041831 0.416186070
K_POINTS automatic
3 3 2 1 1 1
Thanks alot in advance
Tamene Regassa
AAU
Ethiopia
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