LNABLA= .TRUE. | .FALSE.
Usually VASP uses the longitudinal expression for the frequency dependent dielectric matrix as described in the preceeding section (see. 6.72.1). It is however possible to switch to the computationally somewhat simpler transversal expressions by selecting LNABLA=.TRUE. (in this case Eq. (17) and (20) in Ref. ). In this simplification the imaginary part of the macroscopic dielectric function is given by