Artificial Acoustic Shock Wave-Induced Lattice Distortion-Driven Structural Order–Disorder Phase Transition in Natural Polycrystalline Forsterite (α-Mg2SiO4): X-Ray and Raman Spectroscopic Approaches

In the present work, the natural polycrystalline forsterite (α-Mg₂SiO₄) have been chosen for the shock wave recovery experiment which is one of the most prominent silicate group minerals in the upper mantle of the Earth. The analytical techniques such as X-ray diffractometry and Raman spectroscopy have been utilized to extract the impact of shock waves on the olivine samples. According to the observed XRD results, the intensities of uni-indexed diffraction peaks such as (020) and (002) have significantly reduced compared to the bi-indexed (101) and tri-indexed planes (112) at the exposure of 100 shocks. The Raman results demonstrate that the characteristic doublet Raman peaks such as asymmetry and symmetry SiO₄ normalized intensity ratio are found to have reduced and the calculated values are 0.9, 0.9, and 0.72 for 0, 50, and 100 shocks, respectively. Based on the obtained analytical results, the high degree of crystalline nature of α-Mg₂SiO₄ has undergone the structurally disordered state of α-Mg₂SiO₄ phase transition on exposing 100 shocks rather than the crystallographic transitions of β and γ-Mg₂SiO₄. From the results, the prismatic plane (020) has the major contribution to initiating structural revolution of the formation of its high-pressure phases and structurally disordered systems under extreme conditions.