Meyer-Neldel energy in Se-based binary and ternary chalcogenide glasses

The integral equations for DC conductivity and external conductance for the network of localised states in amorphous solids are solved by iteration method. The random free energy barriers and single polaron hopping model are used to obtain the DC conductivity σ _{DC} and Meyer-Neldel energy E_{MN}. The experimental estimates of optical band gap E_g, dielectric function ɛ , glass transition temperature T_g and σ _{DC} are used to calculate E_{MN} for Se-based binary and ternary chalcogenide glasses. The calculated values are found to be in agreement with the available experimental data. E_{MN} increases with increase of attempt frequency. The true pre-exponential factor σ _{00} is related to E_{MN} as ln σ _{00}=p-qE_{MN}, where p is nearly 7.3 and q is material-dependent. The calculated values of E_{MN} and σ _{00} suggest that DC conduction in these chalcogenides is due to acoustic and optical phonon-assisted polaron hopping.