A DFT analysis of enhanced structural, mechanical, elastic tensor analysis, optical, electronic, thermoelectric and magnetic characteristics of X2ScHgCl6 (X=Cs, Rb)

Abstract

This study employs first-principles calculations to investigate the physical properties of X₂ScHgCl₆ (X = Cs or Rb). The mBJ functional is used to ensure accurate and comprehensive analysis on these physical features. The results show that X₂ScHgCl₆ show significant thermodynamic and structural stability. The mechanical properties confirm that both HDPs are mechanically stable, as verified by the Born stability criteria. The positive values of Cauchy pressure (Cp) calculated as 4.09 GPa for Cs₂ScHgCl₆ and 7.09 GPa for Rb₂ScHgCl₆, further indicate the presence of ionic bonding in these materials. To explore their electronic behavior, the band gaps (E_g) and dispersion of electronic states are analysed. Rb₂ScHgCl₆ displays a direct E_g of 2.23 eV in spin-up and 3.57 eV in spin-down states, while Cs₂ScHgCl₆ shows direct E_g of 2.25 eV in spin-down and 3.21 eV in spin-up states, confirming their semiconducting nature. The maximum optical conductivity for Rb₂ScHgCl₆ is calculated to be 5165 1/Ωcm at 12.83 eV, while for Cs₂ScHgCl₆, it is 4595 1/Ωcm at 13.20 eV. The imaginary dielectric ε₂(ω) reveals absorption peaks, reaching a maximum value of at 5.52 eV and for Rb₂ScHgCl₆ and at 5.42 eV for Cs₂ScHgCl₆. The optical conduction shows peaks extending beyond the UV range, indicating that these substances are interesting options for solar energy uses. The high ZT values of 0.91 and 0.90 at 50K for Rb₂ScHgCl₆ and Cs₂ScHgCl₆, respectively, indicate their potential suitability for low-temperature thermoelectric (TE) applications.