First principle calculations of iron and iron-boron transition levels in Si1−xGex alloy Mohammed Alshaikh Hamid Khalafalla and Abdelmadjid Mesli Eur. Phys. J. B, 90 6 (2017) 103 Published online: 05 June 2017 DOI: 10.1140/epjb/e2017-70724-5