High-Pressure Band Structure and Structural Stability of EuTe and EuO Compounds

Abstract A First-Principles method is used to calculate the electronic, structural, and magnetic properties of the semiconductors EuTe and EuO in the rocksalt (RS), cesium chloride (CsCl) and zincblende (ZB) structures, using a self-consistent full-potential linearized augmented plane-wave (FP-LAPW) method within the local-spin-density functional approximation (LSDA) and the generalized gradient approximation (GGA). The program used in our calculation is WIEN2K-2010 code. The effect of pressure on the electronic properties of (EuTe and EuO) was investigated, both compounds showed that the stable structure under normal pressure is rocksalt. Transition under high pressure was estimated for both EuTe and EuO compound from RS structure to CsCl structure, this transition is found to be about 12 GPa, 8 GPa, 10 GPa and 11 GPa for EuTe compound using PBE-GGA, LSDA, WC-GGA and PBEsol-GGA methods respectively, and the transition completed to CsCl structure for EuO compound at about 69 GPa, 61 GPa, 64 GPa and 63 GPa using PBE-GGA, LSDA, WC-GGA and PBEsol-GGA methods respectively. It is found also that these compounds are semiconductors under normal or high pressure conditions in the three structures involved in this study. The band structure calculations showed that EuTe compound has indirect band gap energy in RS and ZB structures, and direct but smaller band gap in CsCl structure. Also EuO band gap energy is indirect in RS and ZB structures but direct in CsCl structure. In addition the comparison between different methods of calculation showed that the PBE-GGA method is better in predicting the lattice constant in the RS structure, but PBEsol-GGA and WC-GGA methods better in predicting the bulk modulus (Bo) and transition pressures (Pt).