[QE-developers] [SPAM] The mathematical formulation of g(:, igk_k(ig, ik)) in epsilon.f90

[Yuvam Bhateja]

Greetings Developers,

I am new to developing QE code and want to understand how it works
internally. I was trying to understand how the epsilon.f90 module works. I
got stuck on how these two lines of code were used in the SUBROUTINE
dipole_calc:

caux = caux + conjg(evc(ig+npwx,iband1))*evc(ig+npwx,iband1)
dipole_aux(:,iband1,iband1) = dipole_aux(:,iband1,iband1) + (
g(:,igk_k(ig,ik))+ xk(:,ik) ) * caux

I couldn't understand this relation between the dipole matrix element
dipole_aux and the reciprocal lattice vector g(:,igk_k(ig,ik))+ xk(:,ik).

I even read the epsilon.x user manual trying to understand the underlying
maths behind this code. I ultimately want to know the mathematical relation
between the epsilon and the reciprocal lattice vector g(:,igk_k(ig,ik))+
xk(:,ik) that is used in this module.

If anyone can please direct me to any source material, developer guide or
papers, it would be great!

Regards,
Yuvam



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09/25/24, 02:16:37 AM
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