EuTMg2 (T = Pd, Ag, Ir, Pt, Au), EuTCd2 (T = Pd, Pt, Au) and CaRhMg2 – intermetallic compounds with orthorhombically distorted tetrahedral magnesium (cadmium) substructures

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Steffen Klenner ◽  
Maximilian Kai Reimann ◽  
Rainer Pöttgen
Keyword(s):  
Valence Electron ◽  
Intermetallic Phases ◽  
Stacking Sequence ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Space Group ◽  
X Ray ◽  
Type Space ◽  
Antiferromagnetic Ordering ◽  
Divalent Europium

Abstract The magnesium- and cadmium-rich intermetallic phases EuTMg2 (T = Rh, Pd, Ag, Ir, Pt, Au), EuTCd2 (T = Pd, Pt, Au) and CaRhMg2 were synthesized from the elements in sealed niobium or tantalum ampoules and with heat treatments in muffle or induction furnaces. The samples were characterized by powder X-ray diffraction and the structures were refined from single crystal X-ray diffractometer data. EuTMg2 (T = Pd, Ag, Pt, Au) and EuTCd2 (T = Pd, Pt, Au) crystallize with the MgCuAl2 type, space group Cmcm, while EuRhMg2, EuIrMg2 and CaRhMg2 adopt the YSiPd2 type, space group Pnma. The striking crystal chemical motif of both series of compounds are networks of puckered Mg(Cd) hexagons in ABAB stacking sequence that derive from the aristotype AlB2; however, with different tiling. Temperature dependent magnetic susceptibility and 151Eu Mössbauer spectroscopic measurements indicate stable divalent europium. Antiferromagnetic ordering sets in at 20.2 (EuIrMg2), 22.3 (EuPdMg2), 21.3 (EuAgMg2), 10.9 (EuPdCd2) and 15.5 K (EuPtCd2), respectively. The stable antiferromagnetic ground states are substantiated by metamagnetic transitions. The 151Eu isomer shifts show a linear correlation with the valence electron count for the whole series of EuTMg2, EuTCd2, EuTIn2 and EuTSn2 phases.

The Stannides EuPd2Sn2, EuPt2Sn2, EuAu2Sn2, and Eu5.4Sn5.6 – Structure and Magnetic Properties

2014 ◽  
Vol 69 (7) ◽  
pp. 775-785 ◽  
Author(s):  
Christian Schwickert ◽  
Florian Winter ◽  
Rainer Pöttgen
Keyword(s):  
Magnetic Hyperfine Field ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Space Group ◽  
X Ray ◽  
Antiferromagnetic Ordering ◽  
Divalent Europium ◽  
Sample Chamber ◽  
Tin Coordination

The europium stannides EuT2Sn2 (T = Pd, Pt, Au) and Eu3Ag5.4Sn5.6 were synthesized by highfrequency melting of the elements in sealed niobium ampoules in a water-cooled sample chamber. All samples were characterized by powder X-ray diffraction. The EuT2Sn2 (T = Pd, Pt, Au) stannides crystallize with the CaBe2Ge2-type structure, space group P4/nmm. The structure of EuPd2Sn2 was refined from single-crystal X-ray diffractometer data: a = 462.44(8), c = 1045.8(3) pm, wR = 0.0402, 237 F2 values and 15 refined variables. The palladium and tin atoms build up a threedimensional [Pd2Sn2] polyanionic network, exclusively with Pd-Sn interactions (261 - 269 pm). The Pd1 and Pd2 atoms have square-pyramidal and tetrahedral tin coordination, respectively. The europium atoms fill large voids within the network. They are coordinated to eight palladium and eight tin atoms. Temperature-dependent magnetic susceptibility studies confirm a stable divalent ground state of the europium atoms. The compounds become ordered antiferromagnetically below 6.3 (EuPd2Sn2), 6.1 (EuPt2Sn2) and 7.7 K (EuAu2Sn2). Eu3Ag5.4Sn5.6 adopts a partially ordered variant of the La3Al11 type, space group Immm, a = 471.33(8), b = 1382.5(4), c = 1032.4(2) pm, wR = 0.0449, 692 F2 values, 30 variables. The three-dimensional [Ag5.4Sn5.6] network shows one silver and one tin site besides two sites with substantial Ag/Sn mixing. The two crystallographically independent europium atoms fill larger and smaller cavities within the [Ag5.4Sn5.6] network. Eu3Ag5.4Sn5.6 also shows divalent europium and antiferromagnetic ordering at TN = 6:9 K. A 151Eu Mössbauer spectrum of Eu3Ag5.4Sn5.6 at 5.2 K shows an isomer shift of δ = −10.61 mms−1, typical for Eu(II) compounds, and a magnetic hyperfine field splitting of BHf = 5.9 T. 119Sn Mössbauer spectra of the four stannides show isomer shifts in the range of δ = 1.78 - 2.20 mms−1, usually observed for tin in intermetallic compounds.

The ternary platinides CaGa5Pt3 and EuGa5Pt3

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Judith Bönnighausen ◽  
Stefan Seidel ◽  
Steffen Klenner ◽  
Rainer Pöttgen
Keyword(s):  
Induction Furnace ◽  
Three Dimensional ◽  
Covalent Bonding ◽  
Intermetallic Phases ◽  
Temperature Dependent ◽  
X Ray ◽  
Antiferromagnetic Ordering ◽  
Divalent Europium ◽  
Experimental Magnetic Moment ◽  
Magnetic Hyperfine Splitting

Abstract The ternary platinides CaGa5Pt3 (a = 2082.5(4), b = 406.05(8), c = 739.2(1) pm) and EuGa5Pt3 (a = 2085.5(5), b = 412.75(9), c = 738.7(1) pm) were synthesized from the elements in sealed high-melting metal tubes in an induction furnace. CaGa5Pt3 and EuGa5Pt3 are isotypic with CeAl5Pt3 and isopointal with the YNi5Si3 type intermetallic phases (space group Pnma, oP36 and Wyckoff sequence c 9). The structure of EuGa5Pt3 was refined from single crystal X-ray diffractometer data: wR2 = 0.0443, 1063 F 2 values and 56 variables. The gallium and platinum atoms build up a three-dimensional [Ga5Pt3]2− polyanionic network in which the europium atoms fill slightly distorted hexagonal prismatic voids. The Ga–Pt distances within the network range from 249 to 271 pm, emphasizing the covalent bonding character. Temperature dependent magnetic susceptibility measurements indicate diamagnetism for CaGa5Pt3 and isotypic BaGa5Pt3. EuGa5Pt3 behaves like a Curie–Weiss paramagnet above 50 K with an experimental magnetic moment of 8.17(1) µB/Eu atom, indicating divalent europium. Antiferromagnetic ordering sets in at T N = 8.5(1) K. The divalent ground state of europium is confirmed by 151Eu Mössbauer spectroscopy. EuGa5Pt3 shows a single signal at 78 K with an isomer shift of −9.89(4) mm s−1. Full magnetic hyperfine splitting with a hyperfine field of 25.0(2) T is observed at 6 K in the magnetically ordered regime.

Magnesium-rich Intermetallics RE3RuMg7 (RE=Y, Nd, Dy, Ho) – Rows of Condensed Ru@RE6/2 Octahedra in Magnesium Matrices

2013 ◽  
Vol 68 (12) ◽  
pp. 1273-1278 ◽  
Author(s):  
Marcel Kersting ◽  
Ute Ch. Rodewald ◽  
Christian Schwickert ◽  
Rainer Pöttgen
Keyword(s):  
Magnetic Susceptibility ◽  
Magnetic Moment ◽  
Small Degree ◽  
Intermetallic Phases ◽  
Metamagnetic Transition ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Antiferromagnetic Ordering ◽  
Experimental Magnetic Moment

The magnesium-rich intermetallic phases RE3RuMg7 (RE=Y, Nd, Dy, Ho) have been synthesized from the elements in sealed niobium ampoules and subsequently characterized by powder X-ray diffraction. The structure of the dysprosium compound was refined on the basis of single-crystal X-ray diffractometer data: Ti6Sn5 type, P63=mmc, a=1019.1(2), c=606.76(9) pm, wR2=0.0159, 439 F2 values, 19 variables. The Mg3 site shows a small degree of Mg3=Dy mixing, leading to the composition Dy3:03RuMg6:97 for the investigated crystal. The striking structural motifs in the Dy3RuMg7 structure are rows of face-sharing Ru@Dy6 octahedra and corner-sharing Mg2@Mg8Dy4 icosahedra. The rows of octahedra form a hexagonal rod-packing, and each rod is enrolled by six rows of the condensed icosahedra. Temperature-dependent magnetic susceptibility measurements of Dy3RuMg7 show Curie-Weiss behavior with an experimental magnetic moment of 10.66(1) µB per Dy atom. Antiferromagnetic ordering is detected at TN =27.5(5) K. The 5 K isotherm shows a metamagnetic transition at a critical field of HC =40 kOe

The Gallium Intermetallics REPdGa3 (RE=La, Ce, Pr, Nd, Sm, Eu) with SrPdGa3-type Structure

2014 ◽  
Vol 69 (11-12) ◽  
pp. 1105-1118 ◽  
Author(s):  
Stefan Seidel ◽  
Oliver Niehaus ◽  
Samir F. Matar ◽  
Oliver Janka ◽  
Birgit Gerke ◽  
...  
Keyword(s):  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Antiferromagnetic Ordering ◽  
Arc Melting ◽  
Divalent Europium ◽  
Band Structure Calculations ◽  
Antiferromagnetic Ground State ◽  
Bonding Characteristics ◽  
Structure Calculations

Abstract The gallium-rich intermetallic phases REPdGa3 (RE=La, Ce, Pr, Nd, Sm, Eu) were obtained by arc-melting of the elements and subsequent annealing for crystal growth. The samples were studied by X-ray diffraction on powders and single crystals. The structures of three crystals were refined from X-ray diffractometer data: SrPdGa3 type, Cmcm, a=634.3(1), b=1027.2(1), c=593.5(1) pm, wR=0.0621, 380 F2 values, 20 variables for CePd0:80(4)Ga3:20(4), a=635.9(1), b=1027.5(1), c=592.0(1) pm, wR=0.1035, 457 F2 values, 19 variables for CePdGa3, and a=640.7(1), b=1038.2(1), c=593.7(1) pm, wR=0.0854, 489 F2 values, 19 variables for EuPdGa3. The REPdGa3 gallides are orthorhombic superstructure variants of the aristotype ThCr2Si2. The palladium and gallium atoms build up polyanionic [PdGa3]δ- networks with Pd-Ga and Ga-Ga distances of 248 - 254 and 266 - 297 pm, respectively, in EuPdGa3. The rare earth atoms fill cavities within the polyanionic networks. They are coordinated by five palladium and twelve gallium atoms. Taking CePdGa3 as an illustrative representative, the band structure calculations show largely dispersive itinerant s, p bands and little dispersive d (Pd) and f (Ce) bands, the latter crossing the Fermi level at large magnitude leading to magnetic instability in a spin-degenerate state and a subsequent antiferromagnetic ground state with a small moment of ±0.36 μB on Ce. The bonding characteristics indicate a prevailing Ce-Ga bonding versus Pd-Ga and Ce-Pd. Temperature-dependent magnetic susceptibility and 151Eu Mössbauer spectroscopic measurements point to stable trivalent lanthanum, cerium, praseodymium, and neodymium, but divalent europium. SmPdGa3 shows intermediate valence. Antiferromagnetic ordering occurs at TN =5.1(5), 7.0(5), 6.3(5), 11.9(5), and 23.0(5) for RE=Ce, Pr, Nd, Sm, and Eu, respectively.

Ternary Antimonides RE4T7Sb6 (RE=Gd–Lu; T =Ru, Rh) with Cubic U4Re7Si6-type Structure

2013 ◽  
Vol 68 (9) ◽  
pp. 971-978 ◽  
Author(s):  
Inga Schellenberg ◽  
Ute Ch. Rodewald ◽  
Christian Schwickert ◽  
Matthias Eul ◽  
Rainer Pöttgen
Keyword(s):  
Magnetic Susceptibility ◽  
Single Crystal ◽  
Magnetic Moment ◽  
Induction Furnace ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Antiferromagnetic Ordering ◽  
Arc Melting ◽  
Intermediate Valent

The ternary antimonides RE4T7Sb6 (RE=Gd-Lu; T =Ru, Rh) have been synthesized from the elements by arc-melting and subsequent annealing in an induction furnace. The samples have been characterized by powder X-ray diffraction. Four structures were refined on the basis of single-crystal X-ray diffractometer data: U4Re7Si6 type, space group Im3m with a=862.9(2) pm, wR2=0.0296, 163 F2 values for Er4Ru7Sb6; a=864.1(1) pm, wR2=0.1423, 153 F2 values for Yb4Ru7Sb6; a=872.0(2) pm, wR2=0.0427, 172 F2 values for Tb4Rh7Sb6; and a=868.0(2) pm, wR2=0.0529, 154 F2 values for Er4Rh7Sb6, with 10 variables per refinement. The structures have T1@Sb6 octahedra and slightly distorted RE@T26Sb6 cuboctahedra as building units. The distorted cuboctahedra are condensed via all trapezoidal faces, and this network leaves octahedral voids for the T1 atoms. The ruthenium-based series of compounds was studied by temperature-dependent magnetic susceptibility measurements. Lu4Ru7Sb6 is Pauli-paramagnetic. The antimonides RE4Ru7Sb6 with RE=Dy, Ho, Er, and Tm show Curie-Weiss paramagnetism. Antiferromagnetic ordering occurs at 10.0(5), 5.1(5) and 4.0(5) K for Dy4Ru7Sb6, Ho4Ru7Sb6 and Er4Ru7Sb6, respectively, while Tm4Ru7Sb6 remains paramagnetic. Yb4Ru7Sb6 is an intermediate-valent compound with a reduced magnetic moment of 3.71(1) μB per Yb as compared to 4.54 μB for a free Yb3+ ion

Quaternary intermetallics RE2Pt3Ga4In (RE=Y, Gd-Tm) – intergrowth structures of NdRh2Sn4 and TiNiSi related slabs

2020 ◽  
Vol 235 (4-5) ◽  
pp. 117-125
Author(s):  
Myroslava Horiacha ◽  
Maximilian K. Reimann ◽  
Jutta Kösters ◽  
Vasyl‘ I. Zaremba ◽  
Rainer Pöttgen
Keyword(s):  
Single Crystals ◽  
High Frequency ◽  
Magnetic Moments ◽  
Intermetallic Phases ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Arc Melting ◽  
Intergrowth Structures ◽  
A Site

AbstractThe quaternary gallium-rich intermetallic phases RE2Pt3Ga4In with RE = Y and Gd-Tm were synthesized by arc-melting of the elements and subsequent annealing. Small single crystals were obtained by high-frequency annealing of the samples in sealed tantalum ampoules. The polycrystalline samples were characterized through their X-ray powder patterns. The RE2Pt3Ga4In phases crystallize with a site ordering variant of the orthorhombic Y2Rh3Sn5 type, space group Cmc 21. The structures of Gd2Pt3Ga4In, Dy2Pt3Ga4.14In0.86, Er2Pt3Ga4.17In0.83 and Tm2Pt3Ga4.21In0.79 were refined from single-crystal X-ray diffraction data. The single crystals reveal small homogeneity ranges RE2Pt3Ga4±xIn1±x. The striking geometrical structural building units are slightly distorted trigonal prisms around the three crystallographically independent platinum atoms: Pt1@RE4Ga2, Pt2@RE2Ga4 and Pt3@RE2Ga2In2. Based on these prismatic building units, the RE2Pt3Ga4In structures can be described as intergrowth variants of TiNiSi and NdRh2Sn4 related structural slabs. Temperature dependent magnetic susceptibility studies of Gd2Pt3Ga4In and Tb2Pt3Ga4In show Curie-Weiss behavior and the experimental magnetic moments confirm stable trivalent gadolinium respectively terbium. Gd2Pt3Ga4In and Tb2Pt3Ga4In order antiferromagnetically at TN = 15.8(1) and 26.0(1) K. Magnetization curves at 3 K show field-induced spin reorientations.

Magnetic properties of the germanides RE3Pt4Ge6 (RE=Y, Pr, Nd, Sm, Gd–Dy)

2017 ◽  
Vol 72 (11) ◽  
pp. 855-864 ◽  
Author(s):  
Fabian Eustermann ◽  
Matthias Eilers-Rethwisch ◽  
Konstantin Renner ◽  
Rolf-Dieter Hoffmann ◽  
Rainer Pöttgen ◽  
...  
Keyword(s):  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Modulated Structure ◽  
X Ray ◽  
Antiferromagnetic Ordering ◽  
Arc Melting ◽  
Pauli Paramagnetism ◽  
Van Vleck Paramagnetism ◽  
Van Vleck ◽  
Vleck Paramagnetism

AbstractThe germanides RE3Pt4Ge6 (RE=Y, Pr, Nd, Sm, Gd–Dy) have been synthesized by arc-melting of the elements followed by inductive annealing to improve the crystallinity and allow for structural order. The compounds have been studied by powder X-ray diffraction; additionally the structure of Y3Pt4Ge6 has been refined from single-crystal X-ray diffractometer data. It exhibits a (3+1)D modulated structure, indicating isotypism with Ce3Pt4Ge6. The crystal structure can be described as an intergrowth between YIrGe2- and CaBe2Ge2-type slabs along [100]. Temperature-dependent magnetic susceptibility measurements showed Pauli paramagnetism for Y3Pt4Ge6 and Curie-Weiss paramagnetism for Pr3Pt4Ge6 and Nd3Pt4Ge6. Sm3Pt4Ge6 exhibits van Vleck paramagnetism, while antiferromagnetic ordering at TN=8.1(1) K and TN=11.0(1) K is observed for Gd3Pt4Ge6 and Tb3Pt4Ge6, respectively.

Antiferromagnetic ordering in the plumbide EuPdPb

2017 ◽  
Vol 72 (12) ◽  
pp. 989-994
Author(s):  
Lukas Heletta ◽  
Steffen Klenner ◽  
Theresa Block ◽  
Rainer Pöttgen
Keyword(s):  
Magnetic Susceptibility ◽  
Magnetic Hyperfine Field ◽  
Metamagnetic Transition ◽  
Muffle Furnace ◽  
Temperature Dependent ◽  
X Ray ◽  
Antiferromagnetic Ordering ◽  
Divalent Europium ◽  
Polycrystalline Form ◽  
Experimental Magnetic Moment

AbstractThe plumbide EuPdPb was synthesized in polycrystalline form by reaction of the elements in a sealed niobium ampoule in a muffle furnace. The structure was refined from single-crystal X-ray diffractometer data: TiNiSi type, Pnma, a=752.4(2), b=476.0(2), c=826.8(2) pm, wR2=0.0485, 704 F2 values and 20 variables. The europium atoms are coordinated by two tilted and puckered Pd3Pb3 hexagons (280–289 pm Pd–Pb) with pronounced Eu–Pd bonding (312–339 pm). Temperature-dependent magnetic susceptibility measurements show Curie-Weiss behaviour and an experimental magnetic moment of 7.35(1) μB per Eu atom. EuPdPb orders antiferromagnetically at TN=13.8(5) K and shows a metamagnetic transition at a critical field of 15 kOe. 151Eu Mössbauer spectra confirm divalent europium (δ=–10.04(1) mm s−1) and show full magnetic hyperfine field splitting (Bhf=21.1(1) T) at 6 K.

Intermetallic Cadmium Compounds M5T2Cd (M = Ca, Yb, Eu; T = Cu, Ag, Au) with Mo5B2Si-type Structure

2011 ◽  
Vol 66 (12) ◽  
pp. 1219-1224
Author(s):  
Frank Tappe ◽  
Christian Schwickert ◽  
Matthias Eul ◽  
Rainer Pöttgen
Keyword(s):  
Magnetic Moments ◽  
Small Degree ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Antiferromagnetic Ordering ◽  
Pauli Paramagnetism ◽  
Slab Temperature ◽  
Experimental Magnetic Moment ◽  
The Eu

The intermetallic compounds M5T2Cd (M = Ca, Yb, Eu; T = Cu, Ag, Au) and Yb5Cu2Zn were synthesized by melting the elements in sealed tantalum tubes followed by annealing at 923 K. All phases were characterized on the basis of powder and single-crystal X-ray diffraction data: Mo5B2Si type, I4/mcm, Z = 4, a = 828.7(1), c = 1528.1(3) pm, wR2 = 0.030, 440 F2 values, 16 variables for Eu5Cu2Cd, a = 788.2(1), c = 1459.3(5) pm, wR2 = 0.053, 378 F2 values, 16 variables for Yb5Cu2Cd, and a = 797.2(1), c = 1438.8(3) pm, wR2 = 0.036, 386 F2 values, 17 variables for Yb5Au2.19Cd0.81, which shows a small degree of Au / Cd mixing. The M5T2Cd structures are intergrowth variants of slightly distorted CuAl2- and U3Si2-related slabs. Striking coordination motifs (exemplary for Eu5Cu2Cd) are square antiprisms of the Eu atoms around Cd, Eu8 square prisms around Eu, and trigonal Eu6 prisms around Cu within the AlB2-related slab. Temperature-dependent magnetic susceptibility measurements showed Pauli paramagnetism for Yb5Cu2Zn, indicating purely divalent ytterbium. Eu5Au2Cd exhibits Curie-Weiss behavior above 100 K with an experimental magnetic moment of 8.14 μB per Eu atom and a Weiss constant of 56 K. Antiferromagnetic ordering of the EuII magnetic moments is evident at 36 K, and a metamagnetic transition is observed at 25 K and 13 kOe.

Structural characterization of zeolite beta

1988 ◽  
Vol 420 (1859) ◽  
pp. 375-405 ◽  
Keyword(s):  
Structural Characterization ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Zeolite Beta ◽  
Computer Assisted ◽  
Hydroxyl Groups ◽  
Stacking Sequence ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray

Crystallographic faulting in zeolite structures affects both the catalytic and sorption properties, and can greatly complicate attempts at structural characterization. A near extreme example of stacking disorder is provided by zeolite beta, a large pore, high-silica zeolite that was first reported in 1967. We describe here the determination of the framework structure of zeolite beta, using primarily high-resolution electron microscopy, electron diffraction, computer-assisted modelling and powder X-ray diffraction. Zeolite beta can be regarded as a highly intergrown hybrid of two distinct, but closely related structures that both have fully three-dimensional pore systems with 12-rings as the minimum constricting apertures. One end member, polymorph A, forms an enantiomorphic pair, space group symmetries P4 1 22 and P4 3 22, with a = 1.25 nm, c = 2.66 nm. Polymorph B is achiral, space group C2/c with a = 1.76 nm, b = 1.78 nm, c = 1.44 nm, β = 114.5°. Both structures are constructed from the same centrosymmetric tertiary building unit (TBU), arranged in layers that, successively, interconnect in either a left- (L) or a right- (R) handed fashion. Polymorph A represents an uninterrupted sequence of RRRR... (or LLLL...) stacking. Polymorph B has an alternating RLRL... stacking sequence. The TBU has no intrinsic preference for either mode of connection, enabling both to occur with almost equal probability in zeolite beta, giving rise to a near random extent of interplanar stacking faults and, to a lesser extent, intraplanar defects terminated by hydroxyl groups. The faulting does not significantly affect the accessible pore volume, but influences the tortuosity of the pore connectivity along the c direction. The high stacking fault densities give rise to complex powder X-ray diffraction (PXD) patterns for zeolite beta materials that comprise both sharp and broad features. By exploiting recursive relations between possible stacking sequences, PXD patterns have been calculated as a function of faulting probability. Reasonable agreement with observed PXD profiles is observed for a ca . 60% faulting probability in the chiral stacking sequence, suggesting a slight preference for polymorph B. The framework building units observed in zeolite beta can also be used to construct other frameworks.

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