study of prba<sub>2</sub>cu<sub>3</sub>o<sub>7 </sub>singularity by density functional theory

in order to study some theories about nonsuperconductivity of prba2cu3o7, based on the density functional theory and with apw+lo/lapw method some calculations for prba2cu3o7 (pr123) and yba2cu3o7 (y123) were performed. the lsda+u approximation was used for pr(4f) orbitals and the effect of changing upr on the band structure, pr(4f)-dos, distribution of electrons on the planes and chains, and pr valence were investigated. comparison of computational results with some experiments shows that a suitable region for upr is a number larger than 0.4 ry. with this selection the band structures of pr123 and y123 near fermi energy are coincident completely. therefore, the theories that present the reason for nonsuperconductivity of pr123 corresponds to the difference of holes number or character of holes in pr123 and y123 were found to be incorrect.