Enhance electron-correlation effect on the ruby multiplet energy dependence on pressure

Abstract

Development of white light-emitting diode (LED) device is especially important due to the lack of red emissions. As candidates for white LED's novel red phosphors, Mn 4+ -doped crystals have received growing attention. Hence, the factors that decide the multiplet energies of d 3 ions such as Mn 4+ and Cr 3+ in crystals are very important to understand. Especially Cr 3+ activated in α-Al 2 O 3 or the well-known ruby has been widely studied for solid-state laser source. Here we calculated the multiplet energies of ruby under different pressures non-empirically. We also investigated the variables that define the correlation between the local structure and the multiplet energy levels. The results show that the first-principles calculations well reproduced the pressure dependence of 2 E transition energy. We found that the behavior of effective Coulomb integral which mainly determines 2 E transition energy is consistent from the point of view of delocalization of the 3d orbitals and decrease of the parameters of the Coulomb repulsion. • Multiplet energies of α-Al2O3: Cr3+ (ruby) under pressure were calculated. • Effect of lattice relaxation and CDC-CC were investigated thoroughly. • The doublet states were red-shifted, while the quartet states were blue-shifted. • The trend of doublet states mainly due to the effective Coulomb integral ( J eff ).