Calculated electronic properties and structural phase transitions of GdN pnictide under hydrostatic pressure

The full-potential linear augmented plane wave method has been used to study the electronic structure, the structural phase transitions, the ground-state x-ray absorption spectroscopy (XAS), and the x-ray magnetic circular dichroism (XMCD) of GdN pnictide under hydrostatic pressure. To produce a satisfactory excited state used to calculate the XAS, it was necessary to describe the Gd 4f electron-electron interaction within the so-called LDA+U method in the mean field approximation. We have shown that the band structure of GdN pnictide is that of a half-metal for the experimental lattice constant. The 5d orbitals of the Gd sites which dominate the GdN low-lying conduction bands are investigated by means of XAS and XMCD calculations, and the results of the L-2,L-3 XAS and XMCD spectra are found to be in good agreement with the experimental results. Total energy calculations performed for the rocksalt, the wurtzite, the zinc blende, and the CsCl structures reveal the richness of the electronic structure of GdN and predict two structural phase transitions: from rocksalt to zinc blende structure for the extended lattice parameter, and from half-metallic rocksalt to a semiconducting wurtzite structure under hydrostatic pressure.