title: Polymorphism in Zintl Phases ACd4Pn3: Modulated Structures of NaCd4Pn3 with Pn = P, As.
abstract: NaCd4P3 and NaCd4As3 were synthesized via short-way transport using the corresponding elements and CdI2 as mineralizer. At room temperature, the two β-polymorphs adopt the RbCd4As3 structure type which has been recently reported for alkali metal (A)-d(10) transition metal (T)-pnictides (Pn). The title compounds crystallize rhombohedrally in space group R3̅m at room temperature and show reversible phase transitions to incommensurately modulated α-polymorphs at lower temperatures. The low-temperature phases are monoclinic and can be described in space group Cm(α0γ)s with q vectors of q = (-0.04,0,0.34) for α-NaCd4P3 and q1 = (-0.02,0,0.34) for α-NaCd4As3. Thermal properties, Raman spectroscopy, and electronic structures have been determined. Both compounds are Zintl phases with band gaps of 1.05 eV for β-NaCd4P3 and ∼0.4 eV for β-NaCd4As3.
authors.affiliation: Department of Chemistry, Synthesis and Characterization of Innovative Materials, Technical University Munich , Lichtenbergstraße 4, 85747 Garching, Germany.
authors.forename: Carolin
authors.initials: C
authors.lastname: Grotz
authors.affiliation: Department of Chemistry, Synthesis and Characterization of Innovative Materials, Technical University Munich , Lichtenbergstraße 4, 85747 Garching, Germany.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Baumgartner
authors.affiliation: Department of Chemistry, Synthesis and Characterization of Innovative Materials, Technical University Munich , Lichtenbergstraße 4, 85747 Garching, Germany.
authors.forename: Katharina M
authors.initials: KM
authors.lastname: Freitag
authors.affiliation: Department of Chemistry, Synthesis and Characterization of Innovative Materials, Technical University Munich , Lichtenbergstraße 4, 85747 Garching, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Baumer
authors.affiliation: Department of Chemistry, Synthesis and Characterization of Innovative Materials, Technical University Munich , Lichtenbergstraße 4, 85747 Garching, Germany.
authors.forename: Tom
authors.initials: T
authors.lastname: Nilges