WPLASMAI
WPLASMAI = [real]
Default: WPLASMAI = 0
Description: WPLASMAI sets the complex shift (in eV) for the Drude term in the dielectric function.
Metallic systems show a characteristic peak at [math]\displaystyle{ \omega=0 }[/math] in the imaginary dielectric function, which originates from intraband transitions. When WPLASMAI>0 in the calculation of the dielectric function with LOPTICS, these intraband transitions are accounted for via the Drude term:
[math]\displaystyle{ \varepsilon(\omega)=1-\frac{\omega_p^2}{\omega(\omega+i \gamma)}. }[/math]
Here, [math]\displaystyle{ \omega_p }[/math] is the plasma frequency and the complex shift [math]\displaystyle{ \gamma }[/math] introduces a Lorentzian broadening of the Drude peak which serves to account for scattering effects due to phonons, impurities, and electron-electron interactions. If WPLASMAI>0, the Drude term is introduced in both the density-density and current-current response functions.