[Wien] volume optimisation of Fe2O3

[Torsten Andersen]

Hello,

are you expecting this on the basis of literature, or on the basis of 
intuition? I would suggest you try +/- 20% with small RMTs and different 
XC-pots. You might also want to increase RMT*kmax, but for a rough 
estimate I would expect your data to be OK.

Best regards,
Torsten Andersen.

Chandrika wrote:
> 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 (A^0 ) = 5.035        c (A^0 ) = 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 ^* K_max  = 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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-- 
Dr. Torsten Andersen        TA-web: http://deep.at/myspace/
AG Hübner, Department of Physics, Kaiserslautern University
http://cmt.physik.uni-kl.de    http://www.physik.uni-kl.de/