Synthesis and Crystal Structures of K₂SnAs₂ and a New Modification of NaAs 

Abstract

Solid state reactions of potassium or sodium with tin and arsenic resulted in the formation of a new ternary Zintl phase, K2SnAs2 (1) and a new modification of the binary Zintl phase NaAs (2), the syntheses and structures we report herein. Compound 1 is described in the orthorhombic space group Cccm with the unit cell dimensions a = 14.653(5), b = 25.415(6), c = 6.953(4) Å, V = 2589(2) Å3 at 203 K, R(int) = 0.1686 and final R values R1 = 0.0780 [I > 2σ(I)); wR2 = 0.1810 (all data)). Compound 2 crystallizes in the monoclinic space group P21/c and accords to the LiAs structure type with the unit cell dimensions a = 6.242(9), b = 5.849(7), c = 11.55(2) Å, β = 117.1(2)°, V = 375(1) Å3 at 173 K, R(int) = 0.0812 and final R values R1 = 0.0677 [I > 2σ(I)); wR2 = 0.1541 (all data).

Ternary arsenides ATt3As3 (A=K, Rb; Tt=Ge, Sn) with layered structures

“…Previously known ternary phases were limited in the A-Ge-As (A = alkali metal) systems (Li 1.67 Ge 0.33 As, A 5 GeAs 3 (A = Na, Cs), K 2 GeAs 2 ) [11,[23][24][25] but more numerous in the A-Sn-As systems (NaSn 2 As 2 , A 2 SnAs 2 (A = Na, K, Rb), A 5 SnAs 3 (A = Na, K), KSnAs, K 6 Sn 3 As 5 ) [7,[12][13][14]19,[25][26][27][28]. The isostructural arsenides ATt 3 As 3 (A = K, Rb; Tt = Ge, Sn) are new phases in these systems.…”

Flux requirements for the growth of RFeAsO (R=rare earth) superconductors

“…The lattice parameters determined with JADE are a = 6.237͑1͒ Å, b = 5.865͑2͒ Å, c = 11.583͑6͒ Å, and ␤ = 116.88͑3͒, which all agree well with the previous report. 14 As illustrated in Fig. 1, reflections from Na 3 As were also observed.…”

“…Figure 1 shows a representative diffraction spectrum for NaAs. Two different structures have been reported for NaAs: NaP structure with the space group P2 1 2 1 2 1 , 13 and LiAs structure with the space group P2 1 / c. 14 The diffraction pattern shown in Fig. 1 could be indexed with monoclinic LiAs structure.…”

Structural, electronic, and elastic properties of K-As compounds: a first principles study

“…These materials show different physical and chemical properties depending on the structure and chemical composition [2][3][4]. For different stoichiometry and structures, they possess a band gap range from 0.1 eV up to 2.5 eV.…”

“…Alkali metal pnictides are a member of the family of Zintl phase which has drawn the attention of scientists in inorganic research for many years [1,2]. These materials show different physical and chemical properties depending on the structure and chemical composition [2][3][4].…”