Abstract This study is devoted to investigating the electronic structure of a LuPO 4 crystal both within the framework of a model with periodic boundary conditions and using a cluster model with a compound tunable embedding potential (CTEP). The strongly bonded (PO 4 ) 3– group is poorly reproduced using standard DFT functionals and even within the CCSD(T) “gold standard” method. It is proposed to consider this group as a “single structural unit” of orthophosphate-type crystals by describing phosphorus in the group with a special type of pseudopotential—“fragment-PP.” Reproducing the crystal structural parameters in calculations with periodic boundary conditions using this pseudopotential improved by a factor of on average 4 (the relative deviation of the unit-cell volume). The use of fragment-PP in the embedded cluster has improved the reproduction of the equilibrium distances between Lu, P, and O atoms (absolute deviation) by a factor of on average 3.
Шахова et al. (Wed,) studied this question.