LSPECTRALGW
LSPECTRALGW = .FALSE. | .TRUE.
| Default: LSPECTRALGW | = .FALSE. | {{{3}}} |
Description: LSPECTRALGW specifies to use the spectral method for calculating the self-energy.
If LSPECTRALGW = .TRUE. is set, the imaginary part of the self-energy [math]\displaystyle{ \Sigma(\omega)= G W }[/math] is calculated from the imaginary part of screened potential [math]\displaystyle{ W(\omega) }[/math] by shifting the poles of [math]\displaystyle{ W }[/math] by [math]\displaystyle{ \pm \epsilon }[/math], where [math]\displaystyle{ \epsilon }[/math] are the poles of the Green's function [math]\displaystyle{ G }[/math]. Generally, LSPECTRALGW affects the compute time very little. QP energies also hardly change when LSPECTRALGW is modified. However, LSPECTRALGW = .TRUE. is usually is slightly more robust, and should be selected for molecules and other systems with flat bands. One the other hand, LSPECTRALGW = .TRUE. seems to converge slightly slower, as the complex shift CSHIFT is decreased. Set this flag, if the QP energies show erratic behavior, for instance, if QP energies or Z-factors are not in the expected range of values.