Electronic structure and luminescence properties of Ca2Ge7O16:Dy3+ I.I. Leonidov, A.V. Ishchenko, E.I. Konstantinova, V.P. Petrov, V.A. Chernyshev and A.E. Nikiforov EPJ Web Conf., 132 (2017) 03027 Published online: 13 December 2016 DOI: 10.1051/epjconf/201713203027