_{2}O

_{3}by performing configuration interaction (CI) calculation using the DVME method [2]. From these results, we expect that the relativistic DVME method can be also applied to rare earth ions. In this study, as a first approach, in order to obtain the LMCT energy for various trivalent RE ions in REO

_{8}

^{13-}cubic model cluster, we performed first-principles calculations using the DVME method and constructed the theoretical energy diagram of the rare earth ions, and compared it with the reported LMCT energies in YPO

_{4}[3] and YAG [4].

[Computational Method] We constructed a 9-atom cluster consisting of the central RE ion and the 8 oxygen ions with O_{h} symmetry (cubic) and 2.4 Å bond length. We considered the ground state configuration 4f* ^{n}*2p

^{48}and one-electron excitation configuration 4f

^{n}^{+1}2p

^{47},

^{ }where

*n*is the number of 4f electrons. In order to improve the computational accuracy, the configuration dependent correction (CDC) was considered. The LMCT energy was calculated as the transition energy from the top of the valence band corresponding to the highest one of the MOs mainly consisting of oxygen 2p orbital to the MO mainly consisting of RE 4f orbital based on the MO calculation using the DV-Xα method and the CI calculation using the DVME method.

[Result] The theoretical LMCT energies calculated with CDC are shown as the diagram in Fig. 1 together with the diagram for the reported values in YPO_{4} and YAG. The figure shows that the reported trend, especially around Eu to Gd, was successfully reproduced by first-principles calculations. The overestimation for Ho to Tm is probably due to the insufficient consideration of electron correlation.

[1] J. Ueda, *et al*,. Appl. Phys. Lett. **104**, 101904, (2014).

[2] K. Ogasawara,* et al*., Phys. Rev. B, **64**, 115413, (2001).

[3] E. Nakazawa, J. Lumin. **100**, 89, (2002).