Theoretical study of the structure and fundamental properties of AZn2N2 (A = Ca, Sr, Ba)

Abstract

The structure, stability, elastic, electronic, and optical properties of trigonal AZn2N2 (A = Ca, Sr, Ba) are simulated and compared in this work. The stability and physical properties of BaZn2N2 are mainly highlighted. According to the calculated results, three compounds are thermodynamically and mechanically stable, and they are brittle materials. The stability of trigonal BaZn2N2 is confirmed by using the different theoretical approaches. The direct band gap transition is allowed at the Γ point for each compound. The predicted direct band gaps are 1.733, 1.507, and 1.510 eV for CaZn2N2, SrZn2N2, and BaZn2N2, respectively. The valence band is mostly composed of the N-2p orbitals, while the conduction band is mainly contributed from the Ca-3d/Sr-4d/Ba-5d orbitals. The results show that the electron shows high mobility for carrier transport, and the value of exciton binding energy is less than 80 meV. Furthermore, compared to CaZn2N2 and SrZn2N2, BaZn2N2 shows excellent light absorption capacity in the visible region. This study indicates that BaZn2N2 is a desirable material for solar cell applications.

Keywords

• AZn2N2
• Stability
• Elastic constant
• Optoelectronic properties
• DFT