The Electric Field Gradients from the On-Site Holes at Cu and O Nuclei in YBa₂Cu₃O₇

Abstract

A consistent explanation of the electric field gradients at Cu and O nuclei in YBa 2 Cu 3 O 7 is obtained provided that on-site 3 d and 2 p holes give the dominant contributions. The number of holes per Cu(2) site in the planer d x 2 - y 2 - p σ antibonding orbital is estimated to be nearly one (that is, the orbital is nearly half-filled), more than half of which are attributed to the oxygen 2 p holes. For oxygen sites, it is necessary to consider both the p σ and p π holes, while more than 80% of 2 p holes reside on the p σ orbitals in all oxygen sites.