Structural, mechanical, electronic and optical properties of half-metallic XFeSi2O6 (X = Li, Na, K) clinopyroxenes: A first-principles investigation

Abstract

Pyroxene structures are ferromagnetic silicates that are found in abundance in the Earth’s crust and upper mantle, which crystallizes in orthorhombic and monoclinic systems. Here, we present a study using first-principles density functional theory approach in analyzing the structural, physical, optical and magnetic properties of XFeSi2O6 (X = Li, Na, K) pyroxenes in a monoclinic phase. The lattice parameters and lattice angles of the simulated structures in a ferromagnetic structural ordering were consistent with the available experimental data. The optical properties suggested that the structures have a high absorption of UV photons, high reflectivity for visible photons, and calculated loss function spectra show the presence of plasmon peaks near 15 eV–17 eV. The NaFeSi2O6 structure was found to be ductile and the KFeSi2O6 structure demonstrated an auxetic nature. All three compounds were found as ferromagnetic half-metals with a magnetic moment of 5.0μB. These properties suggest potential applications of such pyroxenes in optoelectronics and plasmonics.