[Wien] SECLR4 error in large supercells / high number of k points

[Kurt Lejaeghere]

Thank you very much. I am relieved to say that it finally works.

With kind regards and many thanks

Kurt Lejaeghere

Citeren "Peter Blaha" <pblaha at theochem.tuwien.ac.at>:

> I checked your files and could verify the problem.
>
> You have to change in    SRC_lapw1/lopw.f
> ...
>    90                   CONTINUE
>                         IF (HL .LE. 1.0D-3) GOTO 10
> ...
>
> the value of 1.0d-3 to 1.0d-2
>
> Short explanation: This routine attaches to each LO a plane wave (K_n) and
> checks if the basis function (Y_lm * exp(iK_n R) are not linear dependent.
>
> The check was done with a limit of 10-3
>
> It seems, this limit is not secure enough.
>
> PS: A nice example of how one should use the mailing list. Kurt Lejaeghere
> provided convincing arguments and information so that I decided that  
> the problem
> is not due to a user error, but might have deeper roots.
>
> Once I had the example, the solution was not too difficult (in this case).
>
> Thanks for the good "preparation" of the problem.
>
>> I have looked into the matter again and have tried everything I  
>> could think of. Now I am however able to describe the problem more  
>> in detail and more systematically. Tests have shown that the SECLR4  
>> error occurs in all supercells containing bcc Fe and impurities, as  
>> long as the number of k points is high enough. Even if Fe itself is  
>> taken as an impurity, this is the case (the supercell is then pure  
>> iron). When the same size of supercell is taken, the problem always  
>> occurs at the same k point, independent of the value of RKMax or  
>> the chemical nature of the impurity. Most of the times this is the  
>> only k point where the error takes place (a parallel computation  
>> only fails for the subprocess containing that specific k point).  
>> Below an example is given.
>>
>> For a pure Fe supercell containing 128 atoms (4x4x4 supercell, P  
>> sublattice), RKMax 7.0 and 10 k points in the IBZ (200 in the FBZ)  
>> runs without a glitch. When the converged case is restored in a new  
>> and empty directory and the number of k points is increased up to  
>> 56 (2000 in the FBZ), the 2nd k point gives problems (and only that  
>> one):
>>
>>         2         1         1         3        24 24.0
>>
>> The first k point is computed correctly, giving:
>>
>>     K=   0.04167   0.04167   0.04167            1
>>      MATRIX SIZE11270  WEIGHT= 8.00  PGR:
>>     EIGENVALUES ARE:
>>     -5.8279952   -5.8264711   -5.8264711   -5.8264462   -5.8262132
>> (...)
>>      1.9860526    1.9860593    1.9861886    1.9862001    1.9862001
>>      1.9862628    1.9897641    1.9897641    1.9897724    1.9897724
>>      1.9897768    1.9899170    1.9901205    1.9901205    1.9901247
>>            0 EIGENVALUES BELOW THE ENERGY  -10.00000
>>       ********************************************************
>>
>> Afterwards the information of the 2nd k point is printed, resulting in:
>>
>> Matrix size        11235
>>         allocate HS       963.0 MB
>>         allocate Z        342.9 MB
>>     allocate spanel        11.0 MB          dimensions 11235   128
>>     allocate hpanel        11.0 MB          dimensions 11235   128
>> (...)
>>       allocate YL          65.8 MB          dimensions    15 11235    24
>>       allocate phsc         0.2 MB          dimensions 11235
>> Time for los      (hamilt) :         50.8
>> Time for alm         (hns) :          2.9
>> Time for vector      (hns) :         13.5
>> Time for vector2     (hns) :         11.9
>> Time for VxV         (hns) :        265.3
>> Wall Time for VxV    (hns) :          2.1
>> Cholesky INFO =        10819
>>
>> the last line being the SECLR4 error. Because this supercell only  
>> contains identical Fe atoms (at 14 artificially inequivalent  
>> positions) the number of possible changes in the case.in1 file is  
>> limited. Whatever I try, be it -in1ef or -in1_orig, with or without  
>> an additional d-LO, raising or lowering the linearization energies  
>> by 0,1 Ry ..., nothing works and the SECLR4 error persists. With  
>> each test I started from a restore based on the case with 10 k  
>> points, using a new and empty directory.
>>
>> I sincerely hope anyone can help me with this problem, that keeps  
>> hunting me in every supercell I need.
>>
>> With kind regards
>>
>> Kurt Lejaeghere
>> Ghent University, Belgium
>>
>> _______________________________________________
>> Wien mailing list
>> Wien at zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
> -- 
>
>                                       P.Blaha
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
> Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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