First principles investigation of thermoelectric properties of metal halide AgI compoundin zincblende, wurtzite and rock-salt phases

In this thesis, the crystal structures, electronic band structures, phonon distributions and phonon density of states and thermoelectric properties such as Seebeck coefficients, electrical conductivity, electronic thermal conductivity and power factors of AgI were calculated using ab-initio methods for the würtzite and zincblend phases under P = 0 GPa pressure and for the rock-salt phase under three different P = 0, 2, and 10 GPa pressures with or without spin-orbit interaction and for p-type and n-type doping as a function of temperature. For all phases, using semi-classical Boltzmann transport equation under the constant relaxation time approach and considering the lattice thermal conductivity coefficients in the literature, the figure of merit(ZT) calculations result in remarkable values of ZT=1.5 under the pressure of P = 2 GPa for n-type dopping and ZT=2.1 for the p-type doping in the rock-salt phase. Since thermoelectric materials should have a value of ZT> 1 for practical applications, the rock-salt phase of AgI under pressure can be considered as a thermoelectrically promising material.