31052-43-4

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Chemical Properties

white cub crystal(s); -60mesh with 99.5% purity [LID94] [CER91]

InChI:InChI=1/2Rb.Se/q2*+1;-2

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• 7782-49-2 selenium 

Relevant academic research and scientific papers

RbCu1.2Ag3.8Se3 and Cs2Cu2Sb2Se5: Novel Quaternary Intermetallics Synthesized from Superheated Organic Media

Reactions in superheated ethylenediamine (en) solutions at 160°C resulted in two novel quaternary intermetallic copper selenides, RbCu1.2Ag3.8Se3(I) and Cs2Cu2Sb2Se5(II). Both I and II are metal rich and represent new layered structure types. Compound I crystallizes in the tetragonal crystal system, space group P4/nbm (No. 125) with a=5.991(1) A, c=10.918(2) A, Z=2, V=391.9(1) A3, R1/wR2=0.0373/0.0458 for all reflections. Compound II belongs to the triclinic crystal system, space group P1 (No. 2), a=7.645(1) A, b=8.768(2) A, c=10.264(1) A, α=91.97(2)°, β=92.07(2)°, γ=103.05(1)°, Z=2, V=669.2(3) A3, R1/wR2=0.0685/0.0740 for all reflections. I consists of 2∞[(Cu1.2Ag3.8Se 3)-] layers and Rb+ counterions located between these layers. There are two types of metal-to-selenium coordination, a square planar (Ag) and a trigonal pyramidal (Cu/Ag). The Se(1) atom displays an unusual eight coordination with Ag and Cu. II contains alternating 2∞[(Cu2Sb2Se5) 2-] anionic and Cs+ cationic layers. Each copper atom has a distorted tetrahedral coordination to four Se atoms, and each antimony atom bonds to three Se atoms to result in a trigonal pyramidal geometry. Both I and II are semiconductors with estimated band gaps of 0.7-0.8 and 1.2-1.3 eV, respectively.

Impressive Structural Diversity and Polymorphism in the Modular Compounds ABi3Q5 (A = Rb, Cs; Q = S, Se, Te)

An outstanding example of structural diversity and complexity is found in the compounds with the general formula ABi3Q5 (A = alkali metal; Q = chalcogen). γ-RbBi3S5 (I), α-RbBi3Se5 (II), β-RbBi3Se 5 (III), γ-RbBi3Se5 (IV), CsBi 3Se5 (V), RbBi3Se4Te (VI), and RbBi3Se3Te2 (VII) were synthesized from A 2Q (A = Rb, Cs; Q = S, Se) and Bi2Q3 (Q = S, Se or Te) at temperatures above 650 °C using appropriate reaction protocols. γ-RbBi3S5 and α-RbBi3Se 5 have three-dimensional tunnel structures while the rest of the compounds have lamellar structures. γ-RbBi3S5, γ-RbBi3S5, and its isostructural analogues RbBi 3Se4Te and RbBi3Se3Te2 crystallize in the orthorhombic space group Pnma with a = 11.744(2) A, b = 4.0519(5) A, c = 21.081(3) A, R1 = 2.9%, wR2 = 6.3% for (I), a = 21.956(7) A, b = 4.136(2) A, c = 12.357(4), A, R1 = 6.2%, wR2 = 13.5% for (IV), and a = 22.018(3), A, b = 4.2217(6), A, c = 12.614(2) A, R1 = 6.2%, wR2 = 10.3% for (VI). γ-RbBi 3S5 has a three-dimensional tunnel structure that differs from the Se analogues, α-RbBi3Se5 crystallizes in the monoclinic space group C2/m with a = 36.779(4) A, b = 4.1480(5), A, c = 25.363(3), A, β = 120.403(2)o, R1 = 4.9%, wR2 = 9.9%. β-RbBi3Se5 and isostructural CsBi3Se 5 adopt the space group P21/m with a = 13.537(2), A, b = 4.1431(6), A, c = 21.545(3) A, β = 91.297(3)°, R1 = 4.9%, wR2 = 11.0% for (III) and a = 13.603(3), A, b = 4.1502(8) A, c = 21.639(4), A, β = 91.435(3)°, R1 = 6.1%, wR2 = 13.4% for (V). α-RbBi3Se5 is also three-dimensional, whereas β-RbBi3Se5 and CsBi3Se5 have stepped layers with alkali metal ions found disordered in several trigonal prismatic sites between the layers. In γ-RbBi3Se5 and RbBi3Se4Te, the layers consist of Bi 2Te3-type fragments, which are connected in a stepwise manner. In the mixed Se/Te analogue, the Te occupies the chalcogen sites that are on the surface of the layers. All compounds are narrow band-gap semiconductors with optical band gaps ranging 0.4-1.0 eV. The thermal stability of all phases was studied, and it was determined that γ-RbBi 3Se5 is more stable than the and α- and β-forms. Electronic band calculations at the density functional theory (DFT) level performed on α-, β-, and γ-RbBi3Se 5 support the presence of indirect band gaps and were used to assess their relative thermodynamic stability.

Homologous Alkali Metal Copper Rare-Earth Chalcogenides A2Cu2 nLn4Q7+ n(n = 1, 2, 3)

Twenty-seven new members of the A2Cu2nLn4Q7+n (A = Cs, Rb; Ln = La-Nd, Sm, Gd-Yb; Q = S, Se) homologous series were synthesized in one of three structural types (indicated by n = 1, 2, 3). All the compounds contained 3D frameworks with alkali-metal-containing tunnels. For each increment in n, one Cu2Q was added, which was incorporated into the framework as an edge-sharing tetrahedron by replacing a square planar chalcogenide site. High-throughput DFT calculations predicted many of the phases to be thermodynamically stable. These predictions were compared with the synthesis results for the phases formed in each composition space. In the syntheses, heavier lanthanides showed a preference to start forming the n = 3 ACu3Ln2Q5, which is consistent with the predictions. RbCuNd2Se4 and RbCuTb2Se4 were found to be thermally stable under vacuum at temperatures up to 1000 °C. Optical measurements revealed band gaps of 1.55(5) and 1.62(5) eV for CsCuCe2Se4 and RbCuTb2Se4, respectively, and a work function of 4.83(5) eV for CsCuPr2Se4. Additionally, some n = 3 ACu3Ln2Q5 compounds exhibit a negative phonon mode because of a copper atom coordination, which may distort to a trigonal planar geometry at sufficiently low temperatures. The dynamic instabilities and the predicted distortion in the copper tetrahedra for the n = 3 ACu3Ln2Q5 compounds were found to have a linear relationship with the atomic number of the lanthanides and the electronegativity of the lanthanides. The A2Cu2nLn4Q7+n compounds can potentially find application as high-temperature thermoelectric materials and other semiconductors.

Vast Structural and Polymorphic Varieties of Semiconductors AMM′Q4(A = K, Rb, Cs, Tl; M = Ga, In; M′ = Ge, Sn; Q = S, Se)

Nine new chalcogenide semiconductors AInM′Q4 (A+ = K+, Rb+, Cs+, Tl+ M′4+ = Ge4+, Sn4+ Q2- = S2-, Se2-) have been prepared by solid-state syntheses and structurally characterized by single-crystal X-ray diffraction techniques. These new phases fill in the missing links in these quaternary systems and crystallize in various two-dimensional layered polymorphs, while combinations containing large M3+ and M′4+ cations also adopt an extended three-dimensional (3D) network structure. The AMM′Q4 materials exhibit a wide range of band gaps with colored selenides (1.8 eV Eg 2.3 eV) and mostly white sulfides (2.5 eV Eg 3.6 eV). These phases have direct band gaps except for the thallium analogues and the cubic AGaSnSe4-cP84. First-principles theoretical calculations of the electronic band structures reveal critical insight into the structure/property relationships of these materials. The distinct polymorphism of these quaternary phases is studied by discussing kinetic and thermodynamic factors responsible for the crystallization, structural considerations, and complementary density functional theory (DFT) calculations.

Layered and Cubic Semiconductors AGa M′ Q4(A+= K+, Rb+, Cs+, Tl+M′4+= Ge4+, Sn4+Q2-= S2-, Se2-) and High Third-Harmonic Generation

Eighteen new quaternary chalcogenides AGaM′Q4 (A+ = K+, Rb+, Cs+, Tl+ M′4+ = Ge4+, Sn4+ Q2- = S2-, Se2-) have been prepared by solid-state syntheses and structurally characterized using single-crystal X-ray diffraction techniques. These new phases crystallize in a variety of layered structure types. The tin analogues also adopt an extended three-dimensional network structure as polymorphs. The polymorphism and phase-stability in these cases were studied by thermal analysis and high-temperature in situ X-ray powder diffraction. All compounds are semiconductors with the colored selenides absorbing light in the infrared-green region (1.8 eV a large band gap and shows stability under ambient conditions with no significant irradiation damage.

Molecular Germanium selenophosphate salts: Phase-change properties and strong second harmonic generation

A new series of germanium chalcophosphates with the formula A 4GeP4Q12 (A = K, Rb, Cs; Q = S, Se) have been synthesized. The selenium compounds are isostructural and crystallize in the polar orthorhombic space group Pca2s

Helical polymer 1/∞[P2Se62-]: Strong second harmonic generation response and phase-change properties of its K and Rb salts

The selenophosphates A2P2Se6 (A = K, Rb) crystallize in the chiral trigonal space group P3121, with a = 7.2728(9) A, c = 18.872(4) A, and Z = 3 at 298(2) K and a = 14.4916(7) A, c = 18.7999(17) A, and Z = 12 at 173(2) K for K + salt and a = 7.2982(5) A, c = 19.0019(16) A, and Z = 3 at 100(2) K for Rb+ salt. The A2P2Se 6 feature parallel one-dimensional helical chains of 1/∞[P 2Se62-] which depict an oxidative polymerization of the ethane-like [P2Se6]4- anion. On cooling well below room temperature K2P2Se 6 exhibits a displacive phase transition to a crystallographic subgroup and forms a superstructure with a cell doubling along the a- and b-axes. The Rb analogue does not exhibit the phase transition. The compounds are air stable and show reversible glass-crystal phase-change behavior with a band gap red shift of 0.11 and 0.22 eV for K+ and Rb+ salts, respectively. Raman spectroscopy, 31P magic angle spinning solid-state NMR, and pair distribution function (PDF) analysis for crystalline and glassy K2P2Se6 give further understanding of the phase transition and the local structure of the amorphous state. K 2P2Se6 exhibits excellent mid-IR transparency and a strong second harmonic generation (SHG) response. The SHG response is type-I phase-matchable and in the wavelength range of 1000-2000 nm was measured to be 50 times larger than that of the commercially used material AgGaSe 2. Glassy K2P2Se6 also exhibits an SHG response without the application of electric field poling. In connection with the NLO properties the thermal expansion coefficients for K 2P2Se6 are reported.

The noncentrosymmetric chain compounds, A3M2AsSe 11 (A = K, Rb, Cs; M = Nb, Ta)

The noncentrosymmetric niobium and tantalum selenoarsenates, A 3Nb2AsSe11 (A=K, Rb, Cs) and K 3Ta2AsSe11, were synthesized in a polyselenoarsenate flux. All compounds crystallize in the polar monoclinic space group Cc. The structures are comprised of the same type of infinite chain anions, [M2Se2(Se2)3(AsSe 3)]3- (M=Nb, Ta) separated by alkali metal cations. The As3+ centers with nonbonded electron pairs play an important role in stabilizing the noncentrosymmetric structures. UV-Vis spectroscopy, Raman spectroscopy and differential thermal analysis data are reported. The energy gaps of these compounds vary between 1.35 and 1.53eV.

APdCu(Se2)(Se3) (A = K and Rb): New quaternary copper palladium polyselenides with unusual metal-selenium coordination

Two novel metal polyselenides, KPdCu(Se2)(Se3) (I) and RbPdCu(Se2)(Se3) (II), have been synthesized from solvothermal reactions in superheated ethylenediamine at 160 °C. The isostructural compounds crystallize in the monoclinic space group P21/m, Z = 2, with a = 6.145(1) A, b = 7.268(1) A, c = 8.865(2) A, β = 102.41(3)° for I, and a = 6.253(1) A, b = 7.267(1) A, c = 8.993(2) A, β = 102.28(3)° for II. Their crystal structures are two-dimensional networks with ∞2[PdCu(Se2) (Se3)]- anionic layers built from one-dimensional ∞1[Pd(Se2) (Se3)]2- chains that are stitched together by tetrahedrally coordinated Cu atoms. The DSC data show that I and II are stable up to 400 °C and decompose at ca. 436 and 424 °C, respectively. Both compounds are narrow band-gap semiconductors with estimated band gaps of about 0.7 eV (I) and 0.8 eV (II), respectively. They are the first structurally characterized quaternary copper palladium polychalcogenides with a (Se2)2- and a (Se3)2- fragment, both exhibiting interesting and unusual metal-selenium coordination.

K1.10Zr2Se6, Rb0.86Zr2Se6 and Cs0.80Zr2Se6. The first intercalation compounds of zirconium triselenide

Single crystals of K1.10Zr2Se6, Rb0.86Zr2Se6 and Cs0.80Zr2Se6 were obtained by reacting powdered mixtures of A2Se (A = K, Rb, Cs), Zr and Se at 850°C. K1.10Zr2Se6 and Rb0.86Zr2Se6 crystallize in space group Immm (Z = 2), with a = 3.746(3), b = 5.354(8), c = 21.929(3) A and a = 3.756(1), b = 5.354(8), c = 22.81(1) A?, respectively. Cs0.80Zr2Se6 crystallizes in space group Cmc21 (Z = 2), with a = 3.747(1), b = 24.102(5), c = 5.332(2) A?. The compounds are characterized by complex anionic layers ∞2[Zr2Se6]x- with intercalated alkali cations. As in ZrSe3, the layers are built from columns of trigonal prisms ∞1[ZrSe3], connected by additional waist contacts, yielding an eightfold coordination for the Zr atoms. The mean Zr-Se bond lengths correspond to those found in the binary compound. The Se-Se bond lengths are significantly altered, however, indicating a reduction of the Se-Se bond order due to the electron transfer from the alkali metal.