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 minority states are improperly clustered at the Fermi level). It is followed QSGW calculation, using LDA+U as the starting point.

Note: this page is under construction.

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

Input file setup

ErAs forms in the rocksalt structure with a lattice constant 5.408 a₀. However, it is thought to be an antiferromagnet, with Er along the [111] line alternating spins. There for the the unit cell of the rocksalt structure must be doubled to accommodate two inequivalent Er atoms The spin magnetic moment of 3 μ_B. This information is encapsulated in init file below.

Copy the contents in the box below into init.eras. Note that a trial moment of ±3 μ_B is assumed; this will be determined in the course of a self-consistent calculation.

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
      IDMOD=0,1
      INCLUDE ldauparm
      ATOM=Er2 MMOM=0,0,0,-3    PZ=0 0 0 5.5 # Trial spin moment on the f channel
      IDMOD=0,1
      INCLUDE ldauparm
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

Note also the line INCLUDE ldauparm. There is little point in attempting an LDA calculation. We will begin directly with an LDA+U calculation; parameters U and J are supplied in file ldauparm. Copy the contents in the box below into ldauparm.

% ifdef ldau==2
                IDU=0,0,0,112  UH=0,0,0,0  JH=0,0,0,0
% elseif ldau
                IDU= 0 0 0 112 UH= 0 0 0 0.632 JH= 0 0 0 0.055
% endif

Table of Contents

Input file setup