[Pw_forum] one question on |psi|^2

[Paolo Giannozzi]

On Mar 25, 2010, at 11:09 , lfhuang wrote:

>
> |psi|^2 usually denotes the modulus of the wavefucntion, but from  
> the code projwfc.f90, there is
> ......
> proj(nwfc,ibnd,ik)=ABS(proj0(nwfc,ibnd))**2
> ......
> DO nwfc = 1, natomwfc
> psum = psum + proj (nwfc, ibnd, ik)
> END DO
> WRITE( stdout, '(4x,"|psi|^2 = ",f5.3)') psum
> ......
>
> does this mean that |psi|^2 just denote the sum over the moduluses  
> of the weighted atomic orbitals, and the overlaps between atomic  
> orbitals are not accounted? So |psi|^2 is not the modulus of the KS  
> orbital, am I right?

what are you referring to? to |psi^2| as printed in the line above?
or to |psi^2| in general? the latter is 1 by construction; the former
is < 1. What is printed is just a check, for your  convenience. It
tells you how well the projection over atomic states reproduces
the Kohn-Sham orbitals

P.
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Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222