Structural relaxation effects on the electronic excitations and optical properties of Ge nanocrystals embedded in a SiC matrix

We propose a combined method to eciently perform ground- and excited-state calculations for relaxed geometries using both a rst-principles approach and a classical molecular-dynamics scheme. We apply this method to calculate the ground state, the optical properties, and the electronic excitations of Ge nanoparticles embedded in a SiC matrix. Classical dynamics is used to relax the large cell system. First-principles techniques are then used to calculate the electronic structure and, in turn, the electronic excitations and optical properties. The proposed procedure is tested with data resulting from a full rst-principles scheme. Good qualitative accordance has been found between the results after the two computational paths regarding the structure, the optical properties and even the electronic excitations