Site Solution Preference of $\hbox {Bi}^{3+}$ in $\hbox {RE}_{2}\hbox {O}_{3}$ Scintillators

Atomic-scale simulations have been employed to predict the site solution preference of Bi
³⁺
activator cations in a series of RE
₂
O
₃
scintillators with the bixbyite crystal structure (Ialpha3), where RE denotes a 3+ cation ranging in size from Sc
³⁺
to La
³⁺
. There are two crystallographically unique cation sites in the bixbyite structure, in Wyckoff notation referred to as the 24d and 8b site. It is expected that the spectroscopic properties of an activator cation residing on the 24d site will be different from the same activator cation residing on the 8b site, due to the distinct symmetries (C
₂
and S
₆
respectively) of these two sites. Previous studies have revealed two different Bi
³⁺
emissions in Y
₂
O
₃
corresponding to Bi
³⁺
cations occupying both lattice 24d and 8b sites. By predicting the energy difference of the Bi
³⁺
solution on the 24d and 8b sites, we are able to predict the distribution of Bi
³⁺
in a range of bixbyite compounds.