Efficient determination of excitation energies and absorption spectra for quantum dots and large systems from ab initio data

Abstract

A semi-empirical Hamiltonian with the INDO approximation and CIS was parameterized to reproduce EOM-CCSD excitation energies for diatomic silicon Si2 with different inter-atomic separations. The model Hamiltonian is transferable, producing excitation energies for clusters, Sin(n=3,4,5) with mean absolute errors (MAEs) of 0.26, 0.18, and 0.09 eV, respectively, from the EOM-CCSD energies. The absorption spectra are also in qualitative agreement with the EOM-CCSD spectra. For clusters Si19 and Si40, comparison with TDDFT gave MAEs of 0.32 and 0.12 eV, respectively. Predictions of excitation energies and absorption spectra are also given for Sin (n=124,147,172,779) using the model Hamiltonian.