[Pw_forum] About valence bands maximum

[lan haiping]

Dear All,

    I want to determin  the transition enery of a defect level.  It is
important to align the valence bands maximum of different systems under
investigation. Many works  has claimed valence bands maximum alignments were
performed but no technique details are given.
For my understanding,
I thougt the valence bands maxium of charge defect systems could be
determined by aligning its average potential
to pure perfect system's potential, e.g  \epsilon_{VBM}.(Defects,q) =
\epsilon_{VBM}(0) + [<V(D,q)> -<V(0)>].   But some person told me  such
expression has omitted something.    So it really confused me much. As far
as i know,  the potential of system could be only determined  to some
constant . i thought the alignment of average potentials of two systems
could take into account this arbitrariness.. I am not very certain about
this  VBM alignment right now   Would you give me some comments and clarify
my understanding ?

I appreciate any suggestions and comments .

Cheers ,
Hai-Ping




-- 
Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
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