Electronic, optical, thermoelectric and NMR properties of Rb<sub>2</sub>XF<sub>6</sub> (X = Si, Pd) double perovskites for advanced energy recovery applications

Alanazi F. K., Fatmi M., Ghebouli M. A., Bouferrache K., Alomairy S., Abualreish M. J. A., ...Daha Fazla

APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, cilt.132, sa.7, 2026 (SCI-Expanded, Scopus) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 132 Sayı: 7
  • Basım Tarihi: 2026
  • Doi Numarası: 10.1007/s00339-026-09655-3
  • Dergi Adı: APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Aerospace Database, Chemical Abstracts Core, Chimica, Compendex, INSPEC, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO), Materials Science & Engineering Collection (ProQuest), Technology Collection (ProQuest)
  • Recep Tayyip Erdoğan Üniversitesi Adresli: Evet

Özet

We report a comprehensive first-principles investigation of the electronic, optical, and thermoelectric properties of Rb2XF6 (X = Si, Pd) double perovskites using density functional theory (DFT) and BoltzTraP2 transport calculations. The optimized structures crystallize in the cubic Fm (3) over barm phase with lattice parameters of 8.42 angstrom for Rb2SiF6 and 8.38 angstrom for Rb2PdF6, and bulk moduli of 45.2 and 52.8 GPa, confirming their mechanical and chemical stability. Electronic charge density analysis reveals that substituting Si with Pd redistributes electron density at the B-site, driving a transition from semiconducting behavior (indirect band gap of 2.84 eV for Rb2SiF6) to metallic character with partially filled Pd 4d states crossing the Fermi level. Optical calculations demonstrate strong ultraviolet absorption (alpha > 10(5) cm(-1) at 4.5 eV) and refractive indices in the range 1.45-2.12, suggesting potential for UV photodetectors and optical coatings. Thermoelectric transport analysis shows a Seebeck coefficient of 180 mu V/K at 300 K, increasing to 240 mu V/K at 900 K for Rb2SiF6, alongside electrical conductivity values of 2.3 x 10(18) (Omega ms)(-1), indicating promising thermoelectric energy recovery capabilities. These findings highlight the tunability of Rb2XF6 compounds through chemical substitution and position them as promising candidates for dual-function UV optoelectronic and thermoelectric applications. Furthermore, multinuclear NMR experiments (Rb-87, Pd-105/Si-29, and F-19) complement the theoretical results by confirming the high-symmetry Fm (3) over barm structure through the observation of narrow MAS peaks (FWHM approximate to 6 ppm) and characteristic static broadening, particularly for fluorine nuclei. This synergy between theory and experiment strengthens the reliability of the predicted local electronic environments and underscores the value of NMR as a probe for validating perovskite crystal structures.