[QE-users] Computing inner products involving orbitals

[Lorenzo Paulatto]

You can find an example of how H|psi> is done (and the subroutines you 
have to call before to be sure that everything is in place) in 
PP/src/pw2wannier90.f90

I would recommend you compute just <psi_j|H|psi_i> to begin with, and 
verify that it is \epsilon_i \delta_ij

On 07/10/2020 09:15, Matteo Cococcioni wrote:
> Dear Andrew,
> 
> I would first compute | \psi'_l > = U_lm | \psi_m> using some linear 
> algebra routine (as done in the code in many places by summing over 
> plane waves), then compute
> H |\psi'_l > (e.g., using h_psi.f90), finally the product with < \psi'_n |.
> HTH
> 
> Matteo
> 
> 
> Il giorno mer 7 ott 2020 alle ore 04:27 Andrew Xu 
> <andrewaccount at gmail.com <mailto:andrewaccount at gmail.com>> ha scritto:
> 
>     Hi users,
> 
>     I would like to compute < \psi_n | U^\dagger H U | \psi_m>, where H
>     is the KS Hamiltonian, \psi_n, \psi_m are the KS orbitals, and U is
>     some unitary operator, by modifying the source code (not done
>     separately through a separate Python script, for example), and
>     wanted to ask for some advice. I think I can get the \psi_n, \psi_m
>     in reciprocal space, but am not sure how to get the bra-ket.
> 
>     Best regards,
>     Andrew
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> 
> 
> -- 
> Matteo Cococcioni
> Department of Physics
> University of Pavia
> Via Bassi 6, I-27100 Pavia, Italy
> tel +39-0382-987485
> e-mail matteo.cococcioni at unipv.it <mailto:lucio.andreani at unipv.it>
> 
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-- 
Lorenzo Paulatto - Paris