FP-LAPW Calculations Of The Electronic Properties And Structural Phase Transformations In CoO And CdO

In this thesis the Full-Potential Linearized Augmented Plane-Wave (FP-LAPW) method depending on the Density Functional Theory (DFT) was used to find the atomic structures of materials, the electronic properties and to investigate the structural phase transformations of CdO and CoO compounds under high pressure, and to know the conductivity and the ground state for these compounds. In these calculations the gradient generalized approximation (GGA),the local density approximation(LDA), W-Cohen approximation have been used. For CdO, the equations of state (EOS’s) of rocksalt (RS), zincblende (ZB),cesium chloride (CsCl) and wurtzite (WZ) have been calculated. From these EOS’s the transition under high pressure is occurred from rocksalt (RS) to cesium chloride (CsCl), from wurtzite (WZ) to cesium chloride (CsCl), from wurtzite (WZ) to rocksalt (RS), from zincblende (ZB) to rocksalt (RS), from zincblende (ZB) to cesium chloride (CsCl), and from wurtzite (WZ) to zincblende (ZB). The energy band gaps for all structures of CdO have been calculated. It is ~ - 0.5 eV for RS structure, so this structure indicates to be a semimetal. The CsCl structure indicates to be a semimetal too, because its band gap is ~ - 1.1 eV. The energy band gap is ~ 0.1 eV for ZB structure, which means the CdO compound is a semimetal in this structure. And it is ~ 0.1 eV for WZ structure, so the CdO compound is a semimetal too.The structural properties have also been calculated for all structures. We found the rocksalt (RS) structure is the ground state for CdO compound. The same work done for CoO and the same method with the same approximations was used, the equations of state (EOS’s) of rocksalt (RS), zincblende (ZB), and cesium chloride (CsCl), have been calculated. From these EOS’s, the transition under high pressure is occurred from rocksalt (RS) to cesium chloride(CsCl, from zincblende (ZB) to rocksalt (RS), and from zincblende (ZB) to cesium chloride (CsCl). The energy band gaps for all structures of CoO have been calculated. It is(- 0.5- 0.17 eV) for ZB, so this structure indicates a semimetal. It is between (0.771.1 eV) For CsCl, which means the CoO compound is a semimetal in this structure. Finally the energy band gaps is between (0.15 0.42 eV) for RS structure by using LDA and W-Cohen methods, so the structure is semimetal, but it is ~ 0.01 eV by using GGA method, so this structure is a semimetal too. The structural properties have also been calculated for all structures. We found the zincblende (ZB) structure is the ground state for CoO compound.