Pseudopotential description of rare earths in oxides: The case of Er2Si2O7- art. no. 075108

The applicability of ultrasoft pseudopotentials to the problem of rare-eart h incorporation in silicates is investigated using the compound Er2Si2O7 as a test case. It is found that density-functional theory within the general ized gradient approximation provides a good description of the structural p arameters, when treating the Er 4f states as a partially occupied core shel l. The density of states and the distribution of electronic charge are anal yzed, and it is concluded that the presence of Er tends to increase the cov alency of neighboring Si-O bonds.