Collective electronic excitations in Ti and Zr and their dihydrides

The research was funded by the Tomsk Polytechnic University Competitiveness Enhancement Program. I.V.S. acknowledges financial support from the Ministry of Education and Science of the Russian Federation within the governmental program Megagrants (State Task No. 3.9003.2017/220 or 3.9003.2017/9.10). V.M.S. and E.V.C. acknowledge the partial support from the University of the Basque Country UPV/EHU, Grant No. IT-756-13 and the Spanish Ministry of Economy, Industry and Competitiveness MINEICO, Project Nos. FIS2016-76617-P and FIS2016-75862-P. V.M.S. acknowledges project PI2017-30 of the Departamento de Educacion, Politica Linguistica y Cultura of the Basque government.