The structural, mechanical, electronic, optical and thermodynamic properties of t-X3As4 (X = Si, Ge and Sn) by first-principles calculations

The structural, mechanical, electronic, optical and thermodynamic properties of the t-X3As4 (X = Si, Ge and Sn) with tetragonal structure have been investigated by first principles calculations. Our calculated results show that these compounds are mechanically and dynamically stable. By the study of elastic anisotropy, it is found that the anisotropic of the t-Sn3As4 is stronger than that of t-Si3As4 and t-Ge3As4. The band structures and density of states show that the t-X3As4 (Si, Ge and Sn) are semiconductors with narrow band gaps. Based on the analyses of electron density difference, in t-X3As4 As atoms get electrons, X atoms lose electrons. The calculated static dielectric constants, epsilon(1)(0), are 15.5, 20.0 and 15.1 eV for t-X3As4 (X = Si, Ge and Sn), respectively. The Dulong-Petit limit of t-X3As4 is about 10 J mol(-1)K(-1). The thermodynamic stability successively decreases from t-Si3As4 to t-Ge3As4 to t-Sn3As4.