The flag ANTIRES determines whether the Tamm-Dancoff approximation is used or not. The allowed settings are:
|ANTIRES=0||default: Tamm-Dancoff approximation (TDA)|
|ANTIRES=1||yields exact results at at roughly the same cost as TDA|
|ANTIRES=2||beyond Tamm-Dancoff, coupling between positive and negative frequencies|
VASP uses the procedures outlines in Ref.  to include contributions beyond Tamm-Dancoff. Beyond TDA calculations increase the compute time and memory requirements by typically a factor 2.