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# ANTIRES

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Default: **ANTIRES** = 0

Description: The flag ANTIRES determines whether the Tamm-Dancoff approximation is used or not.

- ANTIRES=0 Tamm-Dancoff approximation (TDA)
- ANTIRES=1 yields exact results at ω=0 at roughly the same cost as TDA
- ANTIRES=2 beyond Tamm-Dancoff, coupling between positive and negative frequencies

VASP uses the procedures outlined in reference ^{[1]} to include contributions
beyond Tamm-Dancoff. Beyond TDA calculations increase the computational time and memory requirements by typically a factor of
2.