[Wien] how to use non-default ROTLOC (local rotation matrix)

[Peter Blaha]

> What exactly goes wrong in the Brillouin zone integration when the mesh is not symmetrized?
>  
> And why do I get problems already in dstart - a program which doesn't care about the k-mesh?  (case.outputd is identical to the calculation with the default rotloc from symmetry, but running lapw5 on the clmsum created by dstart gives case.rho which are not identical - most numbers are about the same, but some differ by some %).
>  
> Given the case.struct and case.in2 in my previous mail, and using a full k-mesh, should I be able to run the calculation?

If I understood you correctly, than you used a different locrot matrix, 
but you also changed the LM list (and included "all" LM) ?

If you did just that, my understanding would have been, that dstart gives 
"identical" starting density (when plotting it with lapw5). If it does 
not, I'm a bit surprised (not too much since I never really 
understood how the nonspherical density components where generated), but 
since overlapping spherical densities are still "pretty" spherical, I 
never cared to check this.

k-mesh:
When you look at the electron density of say a single X-point, its density 
does NOT have the symmetry of the crystal (eg. in cubic case, it may 
contain only a px orbital, but no py,pz). Only when adding the equivalent 
X-points (100, 010 and 001) you get a density which is symmetric as it 
should be.

Alternatively one can "symmetrize" via selection of LM. In cubic we would 
only use LM=40, so via the Gaunt selection rules l=1 (p) orbitals do not 
contribute to this "non-spherical" term and the resulting density is 
spherical as it should be.

Of course, the 3rd method would be that of lapwdm, where you "symmetrize 
the wavefunction of his single X-point and "implicitly" sum over all 
X-points.


                                      P.Blaha
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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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