[Wien] error in elastic constants

[Peter Blaha]

Yes, with distortions the symmetry gets lower and you may get different 
multiplicity.

I can see at least ONE rule that you violated:

Used identical RMTs within such calculations. You cannot change RMTs 
from one to the next structure, since your energies become non-comparable.

Your Al-RMT should be much smaller (eg. 2.2) than the U RMT. Still, you 
may need a larger RKMAX of eg. 8 because of the U atom.




On 12/9/19 5:53 PM, prasad jayasena wrote:
> Dear wien2k community
> 
> I wanted to get the elastic constants of a cubic structure using elastic module in wien2k. I completed the calculation I am getting unacceptable values as below
> 
>   in GPa:
> c11=   -36037.828466 c12=    18133.340459 c44=       54.083125
> 
> I used the optimized correct structure file initially. However in the rhomb and tetra structures in the init_elast steps I had a warning " WARNING: Mult not equal. PLEASE CHECK outputnn-file". Since this warning I accepted the "NEW rhomb.struct_nn file" and "NEW tetra.struct_nn file". In those files the atomic positions are different from the initial correct structure file.
> 
> The following is the atomic positions of case.struct
> 
> 14.730415 14.730415 14.730415 90.000000 90.000000 90.000000
> ATOM   1: X=0.37500000 Y=0.87500000 Z=0.37500000
>            MULT= 2          ISPLIT= 2
>         1: X=0.62500000 Y=0.12500000 Z=0.62500000
> U          NPT=  781  R0=0.00000500 RMT=    2.5000   Z: 92.000
> 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=0.50000000
>            MULT= 4          ISPLIT= 4
>        -2: X=0.50000000 Y=0.75000000 Z=0.75000000
>        -2: X=0.75000000 Y=0.75000000 Z=0.50000000
>        -2: X=0.75000000 Y=0.50000000 Z=0.75000000
> Al         NPT=  781  R0=0.00010000 RMT=    2.5000   Z: 13.000
> LOCAL ROT MATRIX:    0.4082483-0.7071068 0.5773503
>                       0.4082483 0.7071068 0.5773503
>                      -0.8164966 0.0000000 0.5773503
>    48      NUMBER OF SYMMETRY OPERATIONS
> 
> 
> 
> rhomb.struct
> 
>              RELA
>   10.415976 10.415976 25.641396 90.000000 90.000000 90.000000
> ATOM  -1: X=0.87500000 Y=0.87500000 Z=0.87500000
>            MULT= 2          ISPLIT= 4
>        -1: X=0.12500000 Y=0.12500000 Z=0.12500000
> U 1        NPT=  781  R0=0.00000500 RMT=    2.5000   Z: 92.0
> 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=0.50000000
>            MULT= 1          ISPLIT= 4
> Al2        NPT=  781  R0=0.00010000 RMT=    2.3900   Z: 13.0
> 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=0.50000000 Z=0.50000000
>            MULT= 3          ISPLIT= 8
>        -3: X=0.50000000 Y=0.50000000 Z=0.00000000
>        -3: X=0.50000000 Y=0.00000000 Z=0.50000000
> Al3        NPT=  781  R0=0.00010000 RMT=    2.3900   Z: 13.0
> LOCAL ROT MATRIX:    0.0000000 0.5000000 0.8660254
>                       0.0000000-0.8660254 0.5000000
>                       1.0000000 0.0000000 0.0000000
>    12      NUMBER OF SYMMETRY OPERATIONS
> 
> tetra.struct
> 
> 
> 10.398674 10.398674 14.779476 90.000000 90.000000 90.000000
> ATOM  -1: X=0.00000000 Y=0.25000000 Z=0.87500000
>            MULT= 2          ISPLIT=-2
>        -1: X=0.00000000 Y=0.75000000 Z=0.12500000
> U 1        NPT=  781  R0=0.00000500 RMT= 2.50000     Z: 92.0
> LOCAL ROT MATRIX:    0.7071068-0.7071068 0.0000000
>                       0.7071068 0.7071068 0.0000000
>                       0.0000000 0.0000000 1.0000000
> ATOM  -2: X=0.50000000 Y=0.50000000 Z=0.00000000
>            MULT= 4          ISPLIT= 8
>        -2: X=0.00000000 Y=0.50000000 Z=0.50000000
>        -2: X=0.75000000 Y=0.25000000 Z=0.25000000
>        -2: X=0.75000000 Y=0.75000000 Z=0.75000000
> Al1        NPT=  781  R0=0.00010000 RMT= 2.38        Z: 13.0
> LOCAL ROT MATRIX:    0.0000000 0.0000000 1.0000000
>                       1.0000000 0.0000000 0.0000000
>                       0.0000000 1.0000000 0.0000000
> 
> 
> Can someone please tell me whether I should not accept these rhomb/tetra.struct file in the calculation? Is this the reason for wrong elastic constants?
> 
> However I couldn't find a way to continue without accepting the new structure for the. Otherwise errors continue in the init step and could not fin a way finish init . I tries both new and old schemes in the setrmt and I am working with wien2k 18.2 version
> 
> I appreciate your support.
> 
> Prasad
>    
> 
> 
> 
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
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