Ab Initio Study of The Electronic Properties of The Quaternary Compounds AgFeSnS 4 , Ag 2 KPS 4 and Ag 2 KSbS 4

Abstract

AgFeSnS4, Ag2KPS4 and Ag2KSbS4 are quaternary materials with the stannite structure, and their electronic properties have been investigated via DFT using the pseudopotential method. The technique used was DFT+U with the Projector Augmented Wave (PAW). For exchange and correlation, the Generalised Gradient Approximation (GGA) was used. The calculations predicted AgFeSnS4 to have semimetallic property with an intermediate Band (IB) of energy width of about 1.0 eV. The IB is sandwich between an intra valence band gap of 1.0 eV and an intra conduction band of 0.2 eV. Ag2KPS4 was predicted to have semiconducting property with a direct band value 0f 2.19 eV. Ag2KSbS4 was also predicted to be a semiconductor with a direct band gap value of 1.67 eV, both materials have their band gap at the ? point of high symmetry. The partial density of states (PDOS) calculation showed that S-3p and Sn-5s dominated IB, Sn-5s dominated the conduction band for AgFeSnS4. For Ag2KPS4, the top valence subband is mainly S-3p while P-3p dominated the bottom of the conduction band. The calculation also showed that Ag2KSbS4 has its top valence band dominated by S-3p while the conduction band bottom was mainly of Sb-4d and Sb-5s.

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