title: Syntheses, crystal structures, optical and theoretical studies of the actinide thiophosphates SrU(PS4)2, BaU(PS4)2, and SrTh(PS4)2.
abstract: Three new actinide thiophosphates, SrU(PS4)2, BaU(PS4)2, and SrTh(PS4)2, have been synthesized by high-temperature solid-state methods, and their crystal structures were determined from single-crystal X-ray diffraction studies. These three isostructural compounds crystallize in a new structure type in space group D4h13-P42/mbc of the tetragonal system. Their structure features infinite one-dimensional chains of ∞1[An(PS4)2(2–)] anions (An = U or Th). Each An atom is coordinated by eight S atoms in a bicapped trigonal prism, and each P atom is tetrahedrally bonded to four S atoms. The compounds are readily charge balanced as Ak2+An4+(P5+(S2–)4)2. Optical studies on single crystals of SrU(PS4)2 and BaU(PS4)2 as well as ground single crystals of SrTh(PS4)2 revealed a direct band gap of 2.13(2) eV and an indirect band gap value of 1.99(2) eV for SrU(PS4)2 and a direct and indirect gap of about 2.28(2) eV for BaU(PS4)2. SrTh(PS4)2 has a relatively large band gap of 3.02(2) eV. DFT calculations for SrU(PS4)2 and BaU(PS4)2 using the HSE functional predict both compounds to be antiferromagnetic and have very similar electronic structures with band gaps of 2.7 eV. The band gap calculated for SrTh(PS4)2 is 3.2 eV.
authors.affiliation: Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: Adel
authors.initials: A
authors.lastname: Mesbah
authors.forename: Jai
authors.initials: J
authors.lastname: Prakash
authors.forename: Jessica C
authors.initials: JC
authors.lastname: Beard
authors.forename: Sébastien
authors.initials: S
authors.lastname: Lebègue
authors.forename: Christos D
authors.initials: CD
authors.lastname: Malliakas
authors.forename: James A
authors.initials: JA
authors.lastname: Ibers