Time dependent equation of motion coupled cluster (EOM-CC) calculations are capable of providing excited-state information over an arbitrarily wide energy range with a lower memory storage requirement compared to comparable frequency domain methods such as conventional EOM-CC. However, the overall computational cost of a time-dependent calculation is higher than that of the frequency domain counterpart due to the cost of the time-integration. This work considers the implementation of the Short Iterative Lanczos(SIL) method as a way of performing the time integration for TD-EOM-CC at a lower cost than other, more naive integration schemes (such as 4<sup>th</sup> order Runge-Kutta [RK4]). We evaluate the computational cost and accuracy of the SIL scheme, relative to RK4, for generating absorption features in a variety of small molecules. SIL- and RK4-derived spectra are nearly indistinguishable, and the SIL scheme can be nearly an order of magnitude more efficient in some cases.

Enhancing the computational efficiency of time-dependent equation-motion coupled-cluster simulations

ACS Fall 2021

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