A first-principles investigation of the properties of two predicted novel structures of Sn3P4

Two novel structures of Sn3P4 (t-Sn3P4 and o-Sn3P4) are presented in this study. For two novel phases, t-Sn3P4 and o-Sn3P4, the stabilities are verified based on the elastic constants and the phonon dispersion spectra. The phonon density of states (PHDOS), band structures, electronic density of states (DOS) and optical properties are investigated using density functional theory (DFT). o-Sn3P4 has better plasticity and stronger anisotropy than t-Sn3P4. The PHDOS in the lower frequency band is mainly derived from Sn atoms, and in the higher band it is mainly from P atoms. The band structure of t-Sn3P4 shows that it is a narrow indirect band gap semiconductor. And o-Sn3P4 presents a metallic characteristics. Below the Fermi level, the total DOS in the valence band originates mainly from P 'p' with the partial contribution from Sn 'p'. The dielectric constants, conductivities, optical absorption, optical reflectivity, and energy loss functions of t-Sn3P4 and o-Sn3P4 are analyzed. For t-Sn3P4, the static dielectric constant is 12.66 F/m, the real part of conductivity reaches the maximum at 4.45 eV, and the peak in the loss function locates at about 15 eV. For o-Sn3P4, in order, they are 47.27 F/m, at 2.59 eV, and at 10.91 eV.