ANTIRES
ANTIRES = 0 | 1 | 2
The flag ANTIRES determines whether the Tamm-Dancoff approximation is used or not. The allowed settings are:
| Default: ANTIRES | = 0 | default: Tamm-Dancoff approximation (TDA) |
| = 1 | yields exact results at ω=1 at roughly the same cost as TDA | |
| = 2 | beyond Tamm-Dancoff, coupling between positive and negative frequencies |
\begin{tabular}{ll} {\tt ANTIRES}=0 & default: Tamm-Dancoff approximation (TDA) \\ {\tt ANTIRES}=1 & yields exact results at $\omega=0$ at roughly the same cost as TDA \\ {\tt ANTIRES}=2 & beyond Tamm-Dancoff, coupling between positive and negative frequencies \end{tabular}
VASP uses the procedures outlined in Ref. \cite{Sander15} to include contributions beyond Tamm-Dancoff. Beyond TDA calculations increase the computational time and memory requirements by typically a factor of 2.