[Pw_forum] momentum matrix element calculation in PWSCF

[yukihiro_okuno at fujifilm.co.jp]

Dear PWSCF developers.

I want to calculate absorption or dielectric (\epsion' or \epsilon'' )  of
materials

I know in order to get optical properties of materials accurately,

Bethe Salpieter equation is recommended, but  for  saving  calculation
time,

we want to do more  simple calculation.

Then, if the momentum operator matrix element ( or transition matrix
element <\phi_{c} | r|  \phi_{v} > )


<\phi_{c}|p|\phi_{v}>  (where \phi_{c} , \phi_{v} is conduction and valence
wave functions, respectively.

                             and p is the momentum operator )

can be calculated, I think dielectric function can be estimated.

Then, are there subroutine in PWSCF to calculate momentum matrix element in
order to estimate the

absorption or dielectric function.

Can  XSpectra be used to estimate the absorption or dielectric function of
the materials ?


Sincerely, Yukihiro Okuno.