Topological constraints-induced radiation shielding efficiency of SiO2 α-cristobalite polymorphism: Signatures from Hirshfeld pseudo-surfaces

Abstract

The paper presents a synergetic and comprehensive investigation into γ-radiation shields properties on SiO2 α-cristobalite subject varying external pressures (0<p < 9.1 GPa). Utilizing crystallographic methods involving γ-rays and Hirshfeld pseudo-surface (HPSs) analyses, we explore the structural responses of SiO2 α-cristobalite to external pressure and its consequent impact on MAC and LAC. The study encompasses a broad energy range (0.015<E < 15.0 MeV), employing online tool for analysis. Our findings reveal that the fundamental shielding characteristics of SiO2 α-cristobalite, including (5.809<MAC<0.021 cm2/g), (3.10 × 1023<Neff< 3.74 × 1023 e/g), (10.32<Zeff<12.43), and (10.79<Zeq<11.56), remain reliable across different polymorphic forms within the energy domain and varying pressures. The LAC values exhibit a clear dependency on both incident photon energies where it's LAC ∈ [0.042 to 11.776] cm−1 as pressure elevated on the crystal. This relationship underscores the influence of pressure-induced changes in crystal density on LAC values. Additionally, changes in lattice parameters (4.975<a<4.599 Å) and bond lengths under pressure contribute to this observed variation in the LAC values. Further analysis of the topological constraints (TCs) (i.e., 1.603<Si⋯O < 1.610 Å, 111.42°<O⋯Si⋯O < 112.00°, and 146.49°<Si⋯O⋯Si < 127.80° bending and twisting angles respectively) reveals defined correlations with LAC values.HPS topological analyses were also employed shed light on valuable insights into the mutual forces of interaction between atoms in the crystal unit cell. Changes in external stress lead to transformations in the HPSs, reflecting the impact of pressure on topological constraints. The evolution of HPS volume (i.e., 179.59-35.24 Å3) and area (i.e., 205.73-161.51 Å2) as well as void's volume (i.e., 10.20-0.17 Å3) and surface area (i.e., 46.10-3.12 Å2) within the crystal lattice is also observed, indicating a direct relationship between HPSs, crystal compactness, electron density and radiation effectiveness. These signatures have been correlated with TCs and thus on the γ-rays shield effectiveness.