Abstract : My activities are in fundamental research in the group of theory of the Laboratoire des Solides Irradiés. It includes the study of the physical properties of some of those materials which are of interest to the CEA, to nuclear research and to nanoelectronics. The objective is to achieve a parameter-free description of processes which control electronic excitations or electronic relaxations. This covers : - The study of the ground state of materials; - The investigation of the properties of the excited state, from the viewpoint of the spectroscopy of valence electrons; - The lattice dynamics, its coupling with phonons, and the effect of electron-phonon coupling on electronic transport and electronic relaxation. These studies involves high performance computing and require computer time from big facilities like the GENCI in France. In the manuscript, I recall first how the inverse dielectric function is calculated within time dependent, density functional theory, and the link with the measurement of the electronic loss function. Theoretical results are presented for titania TiO$_2$ and zirconia ZrO$_2$ which are uncorrelated oxides. Then main theoretical results on optical absorption of cuprous oxide Cu$_2$O and on zirconia ZrO$_2$ are presented. A new interpretation on the kernel which allows to model excitonic effects in time dependent density functional theory is presented. Finally, recent calculations on boron carbides, and in particular B$_4$C are reviewed.