Comment on quantitative model for the superconductivity suppression in R{sub 1-x}Pr{sub x}Ba{sub 2}Cu{sub 3}O{sub 7} with different rare earths

In a recent letter, a model for the electronic structure of R{sub 1-x}Pr{sub x}Ba{sub 2}Cu{sub 3}O{sub 7}, based on the LDA + U scheme was proposed. The T{sub c} suppression by Pr substitution was argued to be due to the transfer of holes from the superconducting CuO pd{sigma} to a dispersive pf{pi} band formed by O2p{sub {pi}} and Pr 4f orbitals. The insulating nature of PrBa{sub 2}Cu{sub 3}O{sub 7} was ascribed to disorder from Ba atoms on the Pr sites. The ac conductivity of the above compound is discussed