[Wien] HOMO-LUMO

[Peter Blaha]

You are probably correct, if I understand you correctly.

 From the scf-file you can see EF and also the "Band-ranges". These 
numbers are in Ry and HOMO/LUMO as well as the gap (HOMO-LUMO) can be 
obtained from them and is even printed explicitly under the label :GAP.
Note: This gap is only "correct", if the VBM/CBM are in your scf-k-mesh, 
otherwise it is too large (shifted meshes may miss Gamma !)

For the band structure, this is the same when you choose Ry units in 
case.insp.
However, when you set eV units, the fermi energy is set to zero and all 
energies in the plot are with respect to this energy zero. Note also 
here: The "gap" is only correct, when you catch the HOMO/LUMO in the 
k-mesh of your bandstructure plot !!

And last but not least: Please remember, the absolute values of 
HOMO-LUMO eigenvalues have NO meaning in a bandstructure code (since 
they depend on an arbitrary E-zero). Only differences matter.

On 10/2/18 5:33 PM, chin Sabsu wrote:
> Dear Experts,
> 
> This query is about how to get HOMO-LUMO from Wien2k.
> 
> Please correct me if I am heading to the wrong calculation.
> 
> 
> We see that the case.bands.agr file gives Fermi energy at VBM ( at top 
> of VBM which we can call HOMO) and next level (CBM) is LUMO.
> 
> But from this band structure or scf file I do not see how to get HOMO-LUMO.
> 
> When we grep :FER,  it gives some value, ie 0.1255649057 Ry
>  From band structure I get CBM= 1.5448 eV or 0.113540665 Ry.
> 
> If we set FER at 0.1255649057 Ry (considering it as VBM or HOMO) then 
> CBM should be 0.1255649057 Ry+0.113540665 Ry =0.2391055707 Ry which we 
> can call LUMO.
> 
> Could you please correct me if I am wrong in this calculation?
> 
> 
> 
> 
> 
> Kind regards
> 
> Chin S.
> 
> 
> 
> 
> 
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
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