An insight into a novel cubic phase SnSe for prospective applications in optoelectronics and clean energy devices

The novel cubic phase pi-SnSe has recently garnered interest in solar cells, optoelectronic devices and thermoelectric applications. In this work we present the structural, electronic, optical, and elastic properties of pi-SnSe using ultrasoft pseudo-potential technique based on density functional theory with local density approximations (LDA) and generalized gradient approximations(GGA). The analysis of band structure provides an indirect bandgap of magnitude 0.799/1.011 eV (LDA/GGA). For the first time, we have calculated elastic constants values which also satisfy the Born stability criteria. The bulk, shear, Young's moduli, Poisson's ratio, Lame's coefficients, average sound velocity and Debye temperature are estimated in the framework of the Voigt-Reuss-Hill approximation. The calculated Bulk modulus is recorded as 61.18/16.33 GPa (LDA/GGA), which matches well with the values extracted from the Birch-Murnaghan equation of state. pi-SnSe can be characterized as an elastically anisotropic material by the analysis and visualization of the directional dependence of bulk, shear and Young's moduli. The calculated Debye temperature (theta(D)) from LDA/GGA is found as 314.86/214.88 K. The thermal conductivity of pi-SnSe could be high due to high Debye temperature as compared to orthorhombic phase of SnSe (theta(D)similar to 210 K). Moreover, the longitudinal and shear wave velocities in three different directions [100], [110] and [111] are also predicted for the first time. These studies provide an insight into various aspects and properties of novel phase cubic SnSe for better understanding and exploitation/design in optoelectronic and energy storage devices. (C) 2017 Elsevier B.V. All rights reserved.