Thesis (M.Sc. (Physics)) --University of Limpopo, 2008 / We present first principles structural, electronic and optical properties investigation of PdS, which are carried out using density functional theory under plane wave pseudopotential method within the local density approximation. We used ultrasoft- pseudopotentials to carry out our calculations. Calculated lattice parameters of the system show excellent agreement with the experimental values. The lattice parameters were observed to decrease linearly with increasing pressure. The density of states and optical properties of PdS have been computed under hydrostatic pressure. The actual size of the band gap remains constant with increasing pressure, whilst the peaks just below and above the Fermi energy moves to the left and to the right respectively. We also investigated the effect of compositional variation on our reflectance by calculating the reflectivity of Pd4-xPtxS4 and Pd4-xNixS4. Since we have different positions for the same concentration, we used the heats of formation to determine the most stable structures and these structures were used to study the effect of compositional variation on our reflectance spectrum. We studied the equation of state (EOS), structure under hydrostatic pressure, and deduced the bulk modulus. It is important to study these properties under such extreme conditions of pressure and temperature as they tend to occur below the earth's surface. Investigation of stability and mechanical properties of binary and ternary compounds from PtS to PdS have been carried out, were the presence of the miscibility gap is still uncertain. We investigate stability of these compounds by studying the heats of formation, elasticity and electronic properties. Our results show no miscibility gap but continuum solid solution between these compounds. A shift of the Fermi energy towards the conduction band is observed at a 50% concentration of Pd and Pt. All the information obtained on PdS is intended to assist in fitting interatomic potentials to enable studies of systems with many atoms.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/762 |
| Date | January 2008 |
| Creators | Monama, Nkwe Oscar |
| Contributors | Ngoepe, P.E. |
| Publisher | University of Limpopo (Turfloop Campus) |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xiii, 81 leaves. : col. ill. |
| Relation |
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