[Wien] Fe slab

Lukasz Plucinski pluto at physics.ucdavis.edu
Sat Jul 5 11:17:20 CEST 2008


Hello Prof. Blaha,

Thank you for the detailed answer. Tonight calculation has converged 
after 52 iterations !!

I think in larger slab its easier to separate surface states. I thought 
there is enough vacuum in my struct file,  I will test this by comparing 
results with different vacuum size.

Lukasz




Peter Blaha wrote:
> Why would you use such a struct file ?
>
> a) With limited experience, start with small models, 5 or 7 layers only.
> b) I don't know how this struct file was created, but for sure a 15 
> layer Fe(001) slab can have inversion symmetry and I'm pretty sure that 
> WIEN should be able to find the proper symmetry (sgroup) when you allow 
> for it.    Remove ALL numbering for atomes (Fe1,2,3,...) and run the 
> initialization. sgroup (or nn in most cases) should always group 2 atoms 
> together (make them equivalent, except the center). sgroup should also 
> shift the atoms along z.
> Your calculations will be 4 times faster when you have inversion symmetry!
> c) When going for thicker slabs, you should also improve your vacuum. It 
> does not make sense to go to a thick slab, but have surface-surface 
> interactions through the vacuum.
> d) k-mesh: why would one use a "2" fold k-mesh in z-direction. With 
> recent WIEN2k versions you can also specify a 21x21x1 mesh for kgen.
> e) Some cases may need more than 40 iterations. As long as it does not 
> diverge, just continue.
> f) Eventually TEMP with some broadening (0.005) may help convergence. 
> However, in particular with magnetic systems, make sure that the 
> broadening does not influence your magnetism and recheck with smaller 
> broadening.
>
> Lukasz Plucinski schrieb:
>   
>> I am trying to do spin-polarized slab calculation on Fe(001). It runs 
>> ok, but does not converge (fluctuates) after 40 iterations. I tried with 
>> up 1000 k-points (21x21x2 - I guess its already too much), 0.05 mixing 
>> factor, and both PBE(96) and W-C(06) GGAs. Other settings default, 
>> spin-polarized calculation right away.
>>
>> Which parameters should I try to change next ?
>>
>> Struct file below.
>>
>> Lukasz
>>
>>
>>
>> Fe-slab-001                                                                    
>>
>> P   LATTICE,NONEQUIV.ATOMS: 
>> 15                                                
>> MODE OF CALC=RELA 
>> unit=ang                                                    
>>   5.416902  5.416902 54.169021 90.000000 90.000000 
>> 90.000000                  
>> ATOM  -1: X=0.00000000 Y=0.00000000 Z=0.10000000
>>           MULT= 1          ISPLIT=-2
>> Fe1        NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM  -2: X=0.50000000 Y=0.50000000 Z=0.15000000
>>           MULT= 1          ISPLIT=-2
>> Fe2        NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM  -3: X=0.00000000 Y=0.00000000 Z=0.20000000
>>           MULT= 1          ISPLIT=-2
>> Fe3        NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM  -4: X=0.50000000 Y=0.50000000 Z=0.25000000
>>           MULT= 1          ISPLIT=-2
>> Fe4        NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM  -5: X=0.00000000 Y=0.00000000 Z=0.30000000
>>           MULT= 1          ISPLIT=-2
>> Fe5        NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM  -6: X=0.50000000 Y=0.50000000 Z=0.35000000
>>           MULT= 1          ISPLIT=-2
>> Fe6        NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM  -7: X=0.00000000 Y=0.00000000 Z=0.40000000
>>           MULT= 1          ISPLIT=-2
>> Fe7        NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM  -8: X=0.50000000 Y=0.50000000 Z=0.45000000
>>           MULT= 1          ISPLIT=-2
>> Fe8        NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM  -9: X=0.00000000 Y=0.00000000 Z=0.50000000
>>           MULT= 1          ISPLIT=-2
>> Fe9        NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM -10: X=0.50000000 Y=0.50000000 Z=0.55000000
>>           MULT= 1          ISPLIT=-2
>> Fe10       NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM -11: X=0.00000000 Y=0.00000000 Z=0.60000000
>>           MULT= 1          ISPLIT=-2
>> Fe11       NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM -12: X=0.50000000 Y=0.50000000 Z=0.65000000
>>           MULT= 1          ISPLIT=-2
>> Fe12       NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM -13: X=0.00000000 Y=0.00000000 Z=0.70000000
>>           MULT= 1          ISPLIT=-2
>> Fe13       NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM -14: X=0.50000000 Y=0.50000000 Z=0.75000000
>>           MULT= 1          ISPLIT=-2
>> Fe14       NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>> ATOM -15: X=0.00000000 Y=0.00000000 Z=0.80000000
>>           MULT= 1          ISPLIT=-2
>> Fe15       NPT=  781  R0=0.00010000 RMT=    2.3450   Z: 
>> 26.0                  
>> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>>                      0.0000000 1.0000000 0.0000000
>>                      0.0000000 0.0000000 1.0000000
>>    8      NUMBER OF SYMMETRY OPERATIONS
>> -1 0 0 0.0000000
>>  0-1 0 0.0000000
>>  0 0 1 0.0000000
>>        1
>> -1 0 0 0.0000000
>>  0 1 0 0.0000000
>>  0 0 1 0.0000000
>>        2
>>  0-1 0 0.0000000
>> -1 0 0 0.0000000
>>  0 0 1 0.0000000
>>        3
>>  0 1 0 0.0000000
>> -1 0 0 0.0000000
>>  0 0 1 0.0000000
>>        4
>>  0-1 0 0.0000000
>>  1 0 0 0.0000000
>>  0 0 1 0.0000000
>>        5
>>  0 1 0 0.0000000
>>  1 0 0 0.0000000
>>  0 0 1 0.0000000
>>        6
>>  1 0 0 0.0000000
>>  0-1 0 0.0000000
>>  0 0 1 0.0000000
>>        7
>>  1 0 0 0.0000000
>>  0 1 0 0.0000000
>>  0 0 1 0.0000000
>>        8
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