First principles study of local electronic and magnetic properties in pure and electron-doped Nd2CuO4

摘要

The local electronic structure of Nd2CuO4 is determined from ab initio cluster calculations in the framework of density functional theory. Spin-polarized calculations with different multiplicities enable a detailed study of the charge and spin density distributions, using clusters that comprise up to 13 copper atoms in the CuO2 plane. Electron doping is simulated by two different approaches and the resulting changes in the local charge distribution are studied in detail and compared to the corresponding changes in hole-doped La2CuO4. The electric field gradient (EFG) at the copper nucleus is investigated and good agreement is found with experimental values. In particular a careful study of the various contributions to the EFG exhibits that the drastic reduction of the main component of the EFG in the electron-doped material with respect to La2CuO4 is due to a reduction of the occupancy of the 3d(3z2-r2) atomic orbital. Furthermore, the chemical shieldings at the copper nucleus are determined and are compared to results obtained from nuclear magnetic resonance (NMR) measurements. The magnetic hyperfine coupling constants are derived from the spin density distribution calculated for different spin multiplicities.