[Wien] volume optimisation of Fe2O3

[Chandrika]

Hello,
I am not able to optimise the structure of Fe2O3. I do not get a minimum with lapw (volumes -8.5 to 9)) as well as lapw with -so (volumes -7 to 4). I used the experimental values for cell parameters so optimum volume ought to be within these ranges.
Inputs were :

a (A0) = 5.035        c (A0) = 13.72  a =b =90.00        d=120.00

Space group:  167_R-3c

Atom 1: Fe   

 RMT=1.9   

Positions:

      X
     Y
     Z
     
      0.3519208
     0.3519208
     0.3519208
     
      0.6480792
     0.6480792
     0.6480792
     
      0.8519208
     0.8519208
     0.8519208
     
      0.1480792
     0.1480792
     0.1480792
     

Atom 2: O

RMT=1.7

Positions:

 

      X
     Y
     Z
     
      0.943752
     0.5562480
     0.25
     
      0.0562480
     0.4437520
     0.75
     
      0.5562480
     0.25
     0.9437520
     
      0.4437520
     0.75
     0.0562480
     
      0.25
     0.9537520
     0.5562480
     
      0.75
     0.0562480
     0.4437520
     

No of symmetry operation =12

NN-Dist =3.62088 (default)

Exchange correlation potential: 13-GGA 

Energy to separate core and semi core = -8.00

RMT * Kmax  = 7.5

 k-points= 600 (optimized)

Without Spin - polarization:

 run_lapw -I -i 20 -ec 0.00001 -cc 0.0001 



Non spin-polarized but with spin-orbit interaction:

run_lapw -so -cc 0.0001.

Thank you for your suggestions,

Chandrika


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