Improving accuracy and efficiency of calculations of photoemission spectra within the many-body perturbation theory

We present an approach to evaluate quasiparticle energies within many-body perturbation theory that substantially improves both the computational efficiency and numerical accuracy of existing techniques. We use the eigenvectors of the static dielectric matrix as a basis for the frequency-dependent density-density response function, and density functional perturbation theory to avoid the explicit calculation of empty electronic states, and storage and inversion of large dielectric matrices. The numerical accuracy of our approach is controlled by a single parameter that can be systematically varied to test the convergence of the computed quasiparticle energies. We discuss the advantages of the technique by presenting the calculations of the vertical ionization potential and electron affinity of several molecules and clusters, including benzene and diamondoids.