Electronic and vibrational spectra of MgO-CoO solid solutions

The UV-VIS diffuse reflectance and IR transmission spectra of MgO-CoO solid solutions show that the frequency of both electronic and vibrational transitions changes with x molar fraction of CoO. In particular: (i) the energy of the 4T1g(P)←4T1g(F), 4A2g(F)←4T1g(F), and 4T2g(F)←4T1g(F) transitions varies linearly with x (compression effect); (ii) the energy of the transition 4T1g→(conduction band) shows a parabolic dependence upon x; (iii) the transverse optical mode (TO) shows a one-mode vibrational behavior, whose dependence upon x is well described by the modified random isodisplacement model (MREI).