Wide-gap electronic structure, UV optical response and thermoelectric transport in lead-free Cs2KGaCl6 double perovskite

Saoudi Z., Ghebouli M., Fatmi M., YAYLACI M., Elkenany E. B., Abu Hammour R., ...Daha Fazla

Materials Today Advances, cilt.32, 2026 (SCI-Expanded, Scopus)

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 32
  • Basım Tarihi: 2026
  • Doi Numarası: 10.1016/j.mtadv.2026.101018
  • Dergi Adı: Materials Today Advances
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Anahtar Kelimeler: Cs2KGaCl6, FP-LAPW, Lead-free double perovskite, Optical properties, Spin–orbit coupling, TB-mBJ, Thermoelectric transport, WIEN2k
  • Recep Tayyip Erdoğan Üniversitesi Adresli: Evet

Özet

Cubic Cs2KGaCl6 is investigated as a lead-free wide-gap double perovskite using an all-electron FP-LAPW WIEN2k framework that combines structural optimization, corrected electronic structure, optical response, semiclassical transport and finite-temperature lattice thermodynamics. The equilibrium volume increases from 2007.01 bohr3 in LDA to 2246.55 bohr3 in GGA-PBE, while the bulk modulus decreases from 32.71 to 23.98 GPa, confirming a comparatively soft chloride lattice. Cs2KGaCl6 is a direct-gap semiconductor at the scalar-relativistic level: the GGA-PBE gap of 3.033 eV increases to 4.905 eV with TB-mBJ. The corresponding electron/hole effective masses are 0.598/2.293 m0 and 1.063/3.461 m0, respectively, evidencing pronounced carrier asymmetry. TB-mBJ also reduces the static dielectric constant from 2.850 to 2.291 and the refractive index from 1.688 to 1.514, consistent with the widened gap. At 300 K, the maximum calculated power factor reaches 1.625 mW m−1 K−2 on the p-type side and 1.225 mW m−1 K−2 on the n-type side. The Slack-derived lattice thermal conductivity decreases with temperature and is treated as a screening estimate. An independent TB-mBJ + SOC reconstruction gives a direct Γ→Γ gap of 4.881 eV. A 2 × 2 × 2 finite-displacement phonon calculation shows no imaginary branches, while the final dense-k elastic constants satisfy the cubic Born criteria, providing complementary dynamical and mechanical stability checks.