# QSGW calculations for ErAs starting from LDA+U

This tutorial presents an LDA+U calculation for ErAs The LDA provides a very poor description of the Er f states (a large number of them are clustered at the Fermi level). It is followed QS_GW_ calculation, using LDA+U as the starting point.

The tutorial starts under the heading “Tutorial”; you can see a synopsis of the commands by clicking on the box below.

blm --nit=20 --nk=6 --gmax=9 --mag --gw eras
nano actrl.eras
cp actrl.eras ctrl.eras
lmfa eras
mpix -np=16 lmf-MPIK ctrl.eras -vnit=20
mpix -np=16 lmf-MPIK ctrl.eras -vnit=1 --rs=1,0 -vldau=t eras
rm mixm.eras
mpix -np=16 lmf-MPIK ctrl.eras -vnit=20 -vldau=t eras
lmfgwd ctrl.eras -vnit=1 -vumix=1 -vldau=t --job=-1
nano GWinput


#### Input file setup

Eras forms in the rocksalt structure with a lattice constant 5.408 a0 and a magnetic moment of 3 μB. To stabilize a nonzero magnetic moment the symmetry must be broken, so we supply a trial moment of 3μB on the f channel.

Cut and paste the contents in the box below into init.eras.

# Init file for antiferromagnetic ErAs
# blm --nit=20 --nk=6 --gmax=9 --mag --gw eras
LATTICE
ALAT=10.83
PLAT=  0.5 0.5 1.0 0.5 1.0 0.5 1.0 0.5 0.5
SPEC
ATOM=Er  MMOM=0,0,0,3     PZ=0 0 0 5.5 # Trial spin moment on the f channel
ATOM=Er2 MMOM=0,0,0,-3    PZ=0 0 0 5.5 # Trial spin moment on the f channel
SITE
ATOM=Er   POS=  0.0   0.0   0.0
ATOM=Er2  POS=  1.0   1.0   1.0
ATOM=As   POS=  0.5   0.5   0.5
ATOM=As   POS=  1.5   1.5   1.5

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