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INFM-CNR DEMOCRITOS Theory@Elettra group, Trieste, Italy
We introduce a method that allows for the calculation of quasi-particle
spectra in the GW approximation in large systems, yet avoiding any explicit
reference to empty one-electron states.
This is achieved first by introducing an optimal basis set for the
polarization operator, then by expressing the irreducible polarization propagator and self-energy operator through a set of linear response equations, which are solved using a Lanczos-chain algorithm.
We first validate our approach by calculating the vertical ionization energies
of the benzene molecule and then show its potential by addressing the spectrum
of a large molecule such as free-base tetraphenylporphyrin.
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