Electronic, mechanical and piezoelectric properties of glass-like complex Na2Si1−xGexO3 (x = 0.0, 0.25, 0.50, 0.75, 1.0)

Abstract

Motivated by our previous work on pristine Na₂SiO₃, we proceeded with calculations on the structural, electronic, mechanical and piezoelectric properties of complex glass-like Na₂Si_1−xGe_xO₃ (x = 0.0, 0.25, 0.50, 0.75, 1.0) by using density functional theory (DFT). Interestingly, the optimized bond lengths and bond angles of Na₂SiO₃ and Na₂GeO₃ resemble each other with high similarity. On doping we report the negative formation energy and feasibility of transition of Na₂SiO₃ → Na₂GeO₃ while the structural symmetry is preserved. Analyzing the electronic profile, we have observed a reduced band gap on increasing x = Ge concentration at Si-sites. All the systems are indirect band gap (Z–Γ) semiconductors. The studied systems have shown mechanical stabilities by satisfying the Born criteria for mechanical stability. The calculated results have shown highly anisotropic behaviour and high melting temperature, which are a signature of glass materials. The piezoelectric tensor (both direct and converse) is computed. The results thus obtained predict that the systems under investigation are potential piezoelectric materials for energy harvesting.