Electronic and thermoelectric properties of AgBi₃Se₅ and AgBi₃S₅ materials: A first-principles study

In this work, the structural, electronic, and thermoelectric properties of the thermoelectric materials AgBi₃S₅ and AgBi₃Se₅ were calculated using Density Functional Theory (DFT). The aim was to determine the total and partial density of states, the Seebeck coefficient, electrical conductivity, thermal conductivity, and the figure of merit for both systems. The electronic properties were studied using the modified Becke-Johnson Tran-Blaha (TB-mBJ) potential (2009) for the exchange-correlation potential. The analysis of the electronic properties shows that the total density of states of AgBi₃S₅ and AgBi₃Se₅ are similar near the Fermi energy. In general, both materials exhibit comparable characteristics, with some higher peaks below the Fermi energy, primarily due to the partial density of states of the Se atoms. The Seebeck coefficient, electrical conductivity, thermal conductivity, and figure of merit of AgBi₃S₅ align with experimental results. Meanwhile, AgBi₃Se₅ exhibits higher figure of merit values in the temperature range of 500 to 800 K, where it also shows an improved Seebeck coefficient. The highest figure of merit value obtained was 0.441 for AgBi₃Se₅ at a temperature of 800 K.