Electronic, mechanical, optical and piezoelectric properties of glass-like sodium silicate (Na 2 SiO 3 ) under compressive pressure.

The structural, mechanical, electronic, optical and piezoelectric properties of Na 2 SiO 3 are studied under varying compressive unidirectional pressure (0-50 GPa with a difference of 10 GPa) using density functional theory (DFT). The calculated structural properties agree well with previously reported results. At 12 GPa, our calculation shows a structural phase transition from orthorhombic Cmc 2 1 to triclinic P 1. The mechanical profile of Na 2 SiO 3 structures under different compressive unidirectional pressures are analysed by calculating the elastic moduli, Poisson's ratio and eigenvalues of stiffness matrix. Our study shows the mechanical stability of the system up to a pressure of 40 GPa. Herein, we have obtained an indirect band gap of 2.97 eV at 0 GPa. Between 0-50 GPa, the band gaps are within the range 2.62 to 3.46 eV. The system in our study possesses a wide band gap and high optical absorption in the UV-Vis range of electromagnetic radiation. The calculated static refractive indices η x , y , z (0) are close to unity suggesting its transparency. For piezoelectric properties, we have reported the total Cartesian polarization. Our calculations have revealed that Na 2 SiO 3 is a promising candidate for optoelectronic devices while its application in ferroelectric and piezoelectric devices could be improved with further research.