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

Abstract

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 in detail and good agreement is found with experimental values. In particular the drastic reduction of the main component of the EFG in the electron-doped material with respect to La2CuO4 is explained by a reduction of the occupancy of the 3d 3z 2 −r 2 atomic orbital. Furthermore, the chemical shieldings at the copper nucleus are determined and are compared to results obtained from NMR measurements. The magnetic hyperfine coupling constants are determined from the spin density distribution.

Determination of doped charge density in superconducting cuprates from NMR or stripes

“…4,5 It is found that doping with electrons predominantly decreases n d but only slightly n p . In other words, the doped electrons in Ln A comparative interpretation of the NQR results from hole-doped and electron-doped cuprates is complicated by several factors: [9][10][11] (i) the EFG at a copper or oxygen nucleus from a hole in its own electron shell (here called "self EFG"); (ii) the EFG from differently charged nearest neighbors in the CuO 2 plane (abreviated "nn EFG"); (iii) the presence or absence of O 2− ions above and beneath Cu 2+ ions-called "apical" oxygen ions-and of O 2− above and beneath O 2− ions in the CuO 2 plane according to the T or T structure; (iv) hybridization of Cu 3d x 2 −y 2 and O 2p σ orbitals leading to covalent bond, (v) deformation of electron shells in the crystal, and (vi) higher-order effects.…”

Ab initio calculations of the electronic structure of cuprates using large scale cluster techniques

“…Previously, we have investigated in Refs. [19,20] the changes of the copper EFG values that occur upon doping in La 2 CuO 4 and in Nd 2 CuO 4 . We found that it is sufficient to concentrate on those MOs which contain partially occupied 3d x 2 −y 2 and 3d 3z 2 −r 2 AOs at the target nucleus.…”

A DFT study on the electronic structure for iridium nitride under high pressure

“…A very important feature of this code is that its accuracy and cost can be tuned in a wide range, from quick exploratory calculations to high quality simulations matching the accuracy of plane-wave methods. approximation (GGA) [22][23][24]. It adopts norm-conserving pseudopotentials using Troullier and Martins scheme in fully nonlocal form and valence electrons described in a basis set, a linear combination of numerical atomic orbital (LCAO).…”