The Chevrel phase HgMo6S8

Salloum, D.; Gougeon, P.; Potel, M.

doi:10.1107/S1600536809012495

inorganic compounds

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Volume 65| Part 5| May 2009| Page i34

doi:10.1107/S1600536809012495

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The Chevrel phase HgMo₆S₈

Diala Salloum,^a Patrick Gougeon ^a ^* and Michel Potel ^a

^aLaboratoire de Chimie du Solide et Inorganique Moléculaire, URA CNRS No. 6511, Université de Rennes I, Avenue du Général Leclerc, 35042 Rennes CEDEX, France
^*Correspondence e-mail: Patrick.Gougeon@univ-rennes1.fr

(Received 16 March 2009; accepted 2 April 2009; online 18 April 2009)

The crystal structure of HgMo₆S₈, mercury(II) hexamolybdenum octasulfide, is based on (Mo₆S₈)S₆ cluster units ( $[\overline{3}]$ symmetry) interconnected through interunit Mo—S bonds. The Hg²⁺ cations occupy large voids between the different cluster units and are covalently bonded to two S atoms. The Hg atoms and one S atom lie on sites with crystallographic $[\overline{3}]$ and 3 symmetry, respectively. Refinement of the occupancy factor of the Hg atom led to the composition Hg_0.973 (3)Mo₆S₈.

Related literature

For isotypic structures, see: Chevrel & Sergent (1982 ). For a previous report on the title compound as a polycrystalline material, see: Tarascon et al. (1983 ). For crystallographic background, see: Becker & Coppens (1974 ); Johnson & Levy (1974 ).

Experimental

Crystal data

Hg_0.973Mo₆S₈
M_r = 1027.3
Trigonal, $[R \overline 3]$
a = 9.4319 (3) Å
c = 10.7028 (3) Å
V = 824.57 (4) Å³
Z = 3
Mo Kα radiation
μ = 21.62 mm⁻¹
T = 293 K
0.08 × 0.07 × 0.06 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: analytical (de Meulenaer & Tompa, 1965 ) T_min = 0.298, T_max = 0.384
5784 measured reflections
1121 independent reflections
1069 reflections with I > 2σ(I)
R_int = 0.044

Refinement

R[F² > 2σ(F²)] = 0.025
wR(F²) = 0.026
S = 1.74
1121 reflections
31 parameters
Δρ_max = 2.64 e Å⁻³
Δρ_min = −1.57 e Å⁻³

Table 1
Selected bond lengths (Å)

Hg1—S1	2.3914 (8)
Mo1—Mo1ⁱ	2.7184 (3)
Mo1—Mo1ⁱⁱ	2.7515 (3)
Mo1—S1	2.4108 (7)
Mo1—S2	2.4236 (6)
Mo1—S2ⁱⁱⁱ	2.4896 (8)
Mo1—S2ⁱⁱ	2.4933 (6)
Mo1—S2^iv	2.4340 (8)
Symmetry codes: (i) -y, x-y, z; (ii) y, -x+y, -z-1; (iii) $[-y-{\script{1\over 3}}, x-y-{\script{2\over 3}}, z+{\script{1\over 3}}]$ ; (iv) x-y, x, -z-1.

Data collection: COLLECT (Nonius, 1998 ); cell refinement: COLLECT; data reduction: EVALCCD (Duisenberg et al., 2003 ); program(s) used to solve structure: SIR97 (Altomare et al., 1999 ); program(s) used to refine structure: JANA2000 (Petříček & Dušek, 2000 ); molecular graphics: DIAMOND (Bergerhoff, 1996 ); software used to prepare material for publication: JANA2000.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809012495/wm2226sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809012495/wm2226Isup2.hkl

checkCIF report

Comment top

The superconducting compound HgMo₆S₈ was first synthesized as a powder sample by Tarascon et al. (1983), but no details were given on its crystal structure. In the present study, we present the crystal structure refinement of HgMo₆S₈ that has been determined from single-crystal X-ray diffraction data. The title compound is isostructural with the hexagonal Chevrel phases MMo₆X₈ where M is a large cation (M = alkali metal, alkaline earth, lanthanide, actinide etc.; X = S, Se, Te) [see, for instance, Chevrel & Sergent (1982)]. As a consequence its crystal structure consists of octahedral Mo₆ clusters surrounded by fourteen sulfur atoms with eight of them forming a distorted cube (i-type ligands) and the remaining six capping the faces of the S₈ cube (a-type ligands). In the structure of HgMo₆S₈, a part of the chalcogen atoms of the Mo₆Sⁱ₈S^a₆ unit are shared according to the formula Mo₆Sⁱ₂S^i-a_6/2S^a-i_6/2 to form the three-dimensional Mo—S network. The Mo₆S₈ cluster unit is centered at Wyckoff position 6b (3 symmetry). The Mo—Mo distances within the Mo₆ clusters are 2.7184 (3) Å for the intra-triangle distances (distances within the Mo₃ triangles formed by the Mo atoms related through the threefold axis) and 2.7515 (3) Å for the inter-triangle distances. Each Mo atom is surrounded by five S atoms (4 S1 and 1 S2) forming a distorted square-based pyramid. The apex of the pyramid is shared with an adjacent unit and thus ensures the three-dimensional cohesion. Consequently, each Mo₆S₈ unit is interconnected to 6 Mo₆S₈ units to form the Mo—S framework. It results from this arrangement that the shortest intercluster Mo1—Mo1 distances between the Mo₆ clusters is 3.2934 (3) Å, indicating only weak metal-metal interaction. The Hg²⁺ cations reside in the large eight-coordinate voids formed by the chalcogen atoms from eight different Mo₆S₈ units. They are covalently bonded to two S2 atoms at a distance of 2.3914 (8) Å.

HgMo₆S₈ was found to be superconducting at 8 K from DC-susceptibility measurements on a batch of single crystals.

Related literature top

For isotypic structures, see: Chevrel & Sergent (1982). For a previous report on the title compound as a polycrystalline material, see: Tarascon et al. (1983). For crystallographic background, see: Becker & Coppens (1974); Johnson & Levy (1974).

Experimental top

HgMo₆S₈ was obtained in three steps involving, first, the syntheses of single-crystal of InMo₆S₈ by solid state reaction, then the preparation of the binary compound Mo₆S₈ by 'chimie douce' methods and, finally, the synthesis of the title compound by inserting mercury into the Mo₆S₈ host structure at low temperatures. Single crystals of InMo₆S₈ were obtained from a stoichiometric mixture of In₂S₃, MoS₂ and Mo. All handlings of materials were done in an argon-filled glove box. The initial mixture (ca 5 g) was cold pressed and loaded into a molybdenum crucible, which was sealed under a low argon pressure using an arc-welding system. The charge was heated at the rate of 300 K/h up to 1773 K, the temperature which was held for six hours, then cooled at 100 K/h down to 1273 K and finally furnace cooled. Mo₆S₈ was obtained by oxidation of single-crystals of InMo₆S₈ by iodine in a glass tube sealed under vacuum. The end of the tube containing the crystals of the In compound and an excess of iodine was placed in a furnace with about 3 cm of the other end sticking out of the furnace, at about room temperature. The furnace was then heated at 523 K for 96 h. At the end of the reaction, crystals of InI₃ and I₂ were obtained at the cooler end of the tube. Finally, HgMo₆S₈ was prepared by diffusion of mercury into crystals of Mo₆S₈ in a silica glass tube sealed under vacuum at 673 K during 96 h.

Computing details top

Data collection: COLLECT (Nonius, 1998); cell refinement: COLLECT (Nonius, 1998); data reduction: EVALCCD (Duisenberg et al., 2003); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: Jana2000 (Petříček & Dušek, 2000); molecular graphics: DIAMOND (Bergerhoff, 1996); software used to prepare material for publication: Jana2000 (Petříček & Dušek, 2000).

Figures top

	Fig. 1. : View of HgMo₆S₈ along [110].
	Fig. 2. : Plot showing the atom-numbering scheme and the interunit linkage of the (Mo₆S₈)S₆ cluster units. Displacement ellipsoids are drawn at the 97% probability level.

(I) top

Crystal data top

Hg_0.973Mo₆S₈	D_x = 6.204 (1) Mg m⁻³
M_r = 1027.3	Mo Kα radiation, λ = 0.71069 Å
Trigonal, R3	Cell parameters from 7043 reflections
Hall symbol: -R 3	θ = 2.0–42.1°
a = 9.4319 (3) Å	µ = 21.62 mm⁻¹
c = 10.7028 (3) Å	T = 293 K
V = 824.57 (4) Å³	Truncated cube, black
Z = 3	0.08 × 0.07 × 0.06 mm
F(000) = 1374

Data collection top

Nonius KappaCCD diffractometer	1121 independent reflections
Radiation source: fine-focus sealed tube	1069 reflections with I > 2σ(I)
Horizontally mounted graphite crystal monochromator	R_int = 0.044
Detector resolution: 9 pixels mm^-1	θ_max = 39.8°, θ_min = 3.1°
ω– and ϕ–scans	h = −16→16
Absorption correction: analytical (de Meulenaer & Tompa, 1965)	k = −16→16
T_min = 0.298, T_max = 0.384	l = −13→19
5784 measured reflections

Refinement top

Refinement on F	Weighting scheme based on measured s.u.'s w = 1/σ²(F)
R[F² > 2σ(F²)] = 0.025	(Δ/σ)_max = 0.001
wR(F²) = 0.026	Δρ_max = 2.64 e Å⁻³
S = 1.74	Δρ_min = −1.57 e Å⁻³
1121 reflections	Extinction correction: B-C type 1 Lorentzian isotropic (Becker & Coppens, 1974)
31 parameters	Extinction coefficient: 0.020681

Crystal data top

Hg_0.973Mo₆S₈	Z = 3
M_r = 1027.3	Mo Kα radiation
Trigonal, R3	µ = 21.62 mm⁻¹
a = 9.4319 (3) Å	T = 293 K
c = 10.7028 (3) Å	0.08 × 0.07 × 0.06 mm
V = 824.57 (4) Å³

Data collection top

Nonius KappaCCD diffractometer	1121 independent reflections
Absorption correction: analytical (de Meulenaer & Tompa, 1965)	1069 reflections with I > 2σ(I)
T_min = 0.298, T_max = 0.384	R_int = 0.044
5784 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.025	31 parameters
wR(F²) = 0.026	Δρ_max = 2.64 e Å⁻³
S = 1.74	Δρ_min = −1.57 e Å⁻³
1121 reflections

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Hg1	0	0	0	0.0339 (4)	0.973 (3)
Mo1	−0.01555 (2)	−0.17363 (2)	−0.394419 (15)	0.00748 (7)
S1	0	0	−0.22344 (8)	0.0113 (2)
S2	−0.03460 (6)	−0.31591 (7)	−0.58775 (4)	0.00933 (17)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Hg1	0.0384 (4)	0.0384 (4)	0.0249 (6)	0.0192 (2)	0	0
Mo1	0.00780 (9)	0.00831 (9)	0.00617 (10)	0.00391 (6)	0.00003 (5)	−0.00036 (5)
S1	0.0126 (2)	0.0126 (2)	0.0088 (3)	0.00628 (12)	0	0
S2	0.0097 (2)	0.0096 (2)	0.0087 (2)	0.00476 (17)	0.00067 (15)	−0.00032 (15)

Geometric parameters (Å, º) top

Hg1—S1	2.3914 (8)	Mo1—Mo1^ix	2.7184 (3)
Hg1—S1ⁱ	2.3914 (8)	Mo1—Mo1^x	2.7515 (3)
Hg1—S2ⁱⁱ	3.2056 (4)	Mo1—Mo1^xi	2.7184 (4)
Hg1—S2ⁱⁱⁱ	3.2056 (4)	Mo1—Mo1^xii	2.7515 (2)
Hg1—S2^iv	3.2056 (7)	Mo1—S1	2.4108 (7)
Hg1—S2^v	3.2056 (7)	Mo1—S2	2.4236 (6)
Hg1—S2^vi	3.2056 (8)	Mo1—S2^xiii	2.4896 (8)
Hg1—S2^vii	3.2056 (8)	Mo1—S2^x	2.4933 (6)
Mo1—Mo1^viii	3.8679 (3)	Mo1—S2^xii	2.4340 (8)
Mo1—Mo1ⁱⁱⁱ	3.2131 (2)

S1—Hg1—S1ⁱ	180	Mo1^x—Mo1—Mo1ⁱⁱⁱ	97.693 (7)
S1—Hg1—S2ⁱⁱ	105.278 (8)	Mo1^x—Mo1—Mo1^ix	90
S1—Hg1—S2ⁱⁱⁱ	74.722 (8)	Mo1^x—Mo1—Mo1^xi	60.398 (8)
S1—Hg1—S2^iv	105.278 (9)	Mo1^x—Mo1—Mo1^xii	59.205 (7)
S1—Hg1—S2^v	74.722 (9)	Mo1^x—Mo1—S1	115.964 (15)
S1—Hg1—S2^vi	105.278 (9)	Mo1^x—Mo1—S2	55.677 (18)
S1—Hg1—S2^vii	74.722 (9)	Mo1^x—Mo1—S2^xiii	138.626 (14)
S1ⁱ—Hg1—S1	180	Mo1^x—Mo1—S2^x	54.776 (13)
S1ⁱ—Hg1—S2ⁱⁱ	74.722 (8)	Mo1^x—Mo1—S2^xii	114.515 (14)
S1ⁱ—Hg1—S2ⁱⁱⁱ	105.278 (8)	Mo1^xi—Mo1—Mo1ⁱⁱⁱ	96.739 (8)
S1ⁱ—Hg1—S2^iv	74.722 (9)	Mo1^xi—Mo1—Mo1^ix	60.000 (8)
S1ⁱ—Hg1—S2^v	105.278 (9)	Mo1^xi—Mo1—Mo1^x	60.398 (8)
S1ⁱ—Hg1—S2^vi	74.722 (9)	Mo1^xi—Mo1—Mo1^xii	90
S1ⁱ—Hg1—S2^vii	105.278 (9)	Mo1^xi—Mo1—S1	55.682 (12)
S2ⁱⁱ—Hg1—S2ⁱⁱⁱ	180	Mo1^xi—Mo1—S2	116.065 (18)
S2ⁱⁱ—Hg1—S2^iv	113.319 (18)	Mo1^xi—Mo1—S2^xiii	135.971 (18)
S2ⁱⁱ—Hg1—S2^v	66.681 (18)	Mo1^xi—Mo1—S2^x	55.48 (2)
S2ⁱⁱ—Hg1—S2^vi	113.319 (17)	Mo1^xi—Mo1—S2^xii	117.362 (19)
S2ⁱⁱ—Hg1—S2^vii	66.681 (17)	Mo1^xii—Mo1—Mo1ⁱⁱⁱ	148.317 (7)
S2ⁱⁱⁱ—Hg1—S2ⁱⁱ	180	Mo1^xii—Mo1—Mo1^ix	60.398 (6)
S2ⁱⁱⁱ—Hg1—S2^iv	66.681 (18)	Mo1^xii—Mo1—Mo1^x	59.205 (7)
S2ⁱⁱⁱ—Hg1—S2^v	113.319 (18)	Mo1^xii—Mo1—Mo1^xi	90
S2ⁱⁱⁱ—Hg1—S2^vi	66.681 (17)	Mo1^xii—Mo1—S1	115.964 (13)
S2ⁱⁱⁱ—Hg1—S2^vii	113.319 (17)	Mo1^xii—Mo1—S2	57.184 (12)
S2^iv—Hg1—S2ⁱⁱ	113.319 (18)	Mo1^xii—Mo1—S2^xiii	133.837 (19)
S2^iv—Hg1—S2ⁱⁱⁱ	66.681 (18)	Mo1^xii—Mo1—S2^x	113.894 (15)
S2^iv—Hg1—S2^v	180	Mo1^xii—Mo1—S2^xii	55.318 (14)
S2^iv—Hg1—S2^vi	113.319 (19)	S1—Mo1—S2	170.65 (2)
S2^iv—Hg1—S2^vii	66.681 (19)	S1—Mo1—S2^xiii	93.53 (2)
S2^v—Hg1—S2ⁱⁱ	66.681 (18)	S1—Mo1—S2^x	90.323 (17)
S2^v—Hg1—S2ⁱⁱⁱ	113.319 (18)	S1—Mo1—S2^xii	91.758 (14)
S2^v—Hg1—S2^iv	180	S2—Mo1—S2^xiii	95.79 (2)
S2^v—Hg1—S2^vi	66.681 (19)	S2—Mo1—S2^x	87.39 (2)
S2^v—Hg1—S2^vii	113.319 (19)	S2—Mo1—S2^xii	88.750 (19)
S2^vi—Hg1—S2ⁱⁱ	113.319 (17)	S2^xiii—Mo1—S2	95.79 (2)
S2^vi—Hg1—S2ⁱⁱⁱ	66.681 (17)	S2^xiii—Mo1—S2^x	99.70 (2)
S2^vi—Hg1—S2^iv	113.319 (19)	S2^xiii—Mo1—S2^xii	91.39 (2)
S2^vi—Hg1—S2^v	66.681 (19)	S2^x—Mo1—S2	87.39 (2)
S2^vi—Hg1—S2^vii	180	S2^x—Mo1—S2^xiii	99.70 (2)
S2^vii—Hg1—S2ⁱⁱ	66.681 (17)	S2^x—Mo1—S2^xii	168.58 (2)
S2^vii—Hg1—S2ⁱⁱⁱ	113.319 (17)	S2^xii—Mo1—S2	88.750 (19)
S2^vii—Hg1—S2^iv	66.681 (19)	S2^xii—Mo1—S2^xiii	91.39 (2)
S2^vii—Hg1—S2^v	113.319 (19)	S2^xii—Mo1—S2^x	168.58 (2)
S2^vii—Hg1—S2^vi	180	Hg1—S1—Mo1	139.382 (14)
Mo1^viii—Mo1—Mo1ⁱⁱⁱ	133.459 (8)	Hg1—S1—Mo1^ix	139.382 (13)
Mo1^viii—Mo1—S1	85.136 (14)	Hg1—S1—Mo1^xi	139.382 (14)
Mo1^viii—Mo1—S2	85.600 (16)	Mo1—S1—Mo1^ix	68.64 (2)
Mo1^viii—Mo1—S2^xiii	176.394 (13)	Mo1—S1—Mo1^xi	68.64 (2)
Mo1^viii—Mo1—S2^x	83.677 (18)	Mo1^ix—S1—Mo1	68.64 (2)
Mo1^viii—Mo1—S2^xii	85.310 (16)	Mo1^ix—S1—Mo1^xi	68.64 (2)
Mo1ⁱⁱⁱ—Mo1—Mo1^viii	133.459 (8)	Mo1^xi—S1—Mo1	68.64 (2)
Mo1ⁱⁱⁱ—Mo1—Mo1^ix	147.479 (10)	Mo1^xi—S1—Mo1^ix	68.64 (2)
Mo1ⁱⁱⁱ—Mo1—Mo1^x	97.693 (7)	Hg1^xiv—S2—Mo1	125.450 (18)
Mo1ⁱⁱⁱ—Mo1—Mo1^xi	96.739 (8)	Hg1^xiv—S2—Mo1^x	98.407 (18)
Mo1ⁱⁱⁱ—Mo1—Mo1^xii	148.317 (7)	Hg1^xiv—S2—Mo1^xv	97.225 (18)
Mo1ⁱⁱⁱ—Mo1—S1	92.988 (11)	Hg1^xiv—S2—Mo1^xii	156.59 (2)
Mo1ⁱⁱⁱ—Mo1—S2	92.457 (12)	Mo1—S2—Mo1^x	69.005 (19)
Mo1ⁱⁱⁱ—Mo1—S2^xiii	49.898 (13)	Mo1—S2—Mo1^xv	132.74 (2)
Mo1ⁱⁱⁱ—Mo1—S2^x	49.797 (18)	Mo1—S2—Mo1^xii	68.041 (15)
Mo1ⁱⁱⁱ—Mo1—S2^xii	141.203 (18)	Mo1^x—S2—Mo1	69.005 (19)
Mo1^ix—Mo1—Mo1ⁱⁱⁱ	147.479 (10)	Mo1^x—S2—Mo1^xv	129.09 (2)
Mo1^ix—Mo1—Mo1^x	90	Mo1^x—S2—Mo1^xii	66.955 (19)
Mo1^ix—Mo1—Mo1^xi	60.000 (8)	Mo1^xv—S2—Mo1	132.74 (2)
Mo1^ix—Mo1—Mo1^xii	60.398 (6)	Mo1^xv—S2—Mo1^x	129.09 (2)
Mo1^ix—Mo1—S1	55.682 (11)	Mo1^xv—S2—Mo1^xii	80.305 (15)
Mo1^ix—Mo1—S2	117.489 (13)	Mo1^xii—S2—Mo1	68.041 (15)
Mo1^ix—Mo1—S2^xiii	131.337 (14)	Mo1^xii—S2—Mo1^x	66.955 (19)
Mo1^ix—Mo1—S2^x	115.28 (2)	Mo1^xii—S2—Mo1^xv	80.305 (15)
Mo1^ix—Mo1—S2^xii	57.566 (18)

Symmetry codes: (i) −x, −y, −z; (ii) x+1/3, y+2/3, z+2/3; (iii) −x−1/3, −y−2/3, −z−2/3; (iv) −y−2/3, x−y−1/3, z+2/3; (v) y+2/3, −x+y+1/3, −z−2/3; (vi) −x+y+1/3, −x−1/3, z+2/3; (vii) x−y−1/3, x+1/3, −z−2/3; (viii) −x, −y, −z−1; (ix) −y, x−y, z; (x) y, −x+y, −z−1; (xi) −x+y, −x, z; (xii) x−y, x, −z−1; (xiii) −y−1/3, x−y−2/3, z+1/3; (xiv) x−1/3, y−2/3, z−2/3; (xv) −x+y+1/3, −x−1/3, z−1/3.

Experimental details

Crystal data
Chemical formula	Hg_0.973Mo₆S₈
M_r	1027.3
Crystal system, space group	Trigonal, R3
Temperature (K)	293
a, c (Å)	9.4319 (3), 10.7028 (3)
V (Å³)	824.57 (4)
Z	3
Radiation type	Mo Kα
µ (mm⁻¹)	21.62
Crystal size (mm)	0.08 × 0.07 × 0.06

Data collection
Diffractometer	Nonius KappaCCD diffractometer
Absorption correction	Analytical (de Meulenaer & Tompa, 1965)
T_min, T_max	0.298, 0.384
No. of measured, independent and observed [I > 2σ(I)] reflections	5784, 1121, 1069
R_int	0.044
(sin θ/λ)_max (Å⁻¹)	0.900

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.025, 0.026, 1.74
No. of reflections	1121
No. of parameters	31
No. of restraints	?
Δρ_max, Δρ_min (e Å⁻³)	2.64, −1.57

Computer programs: COLLECT (Nonius, 1998), EVALCCD (Duisenberg et al., 2003), SIR97 (Altomare et al., 1999), Jana2000 (Petříček & Dušek, 2000), DIAMOND (Bergerhoff, 1996).

Selected bond lengths (Å) top

Hg1—S1	2.3914 (8)	Mo1—S2	2.4236 (6)
Mo1—Mo1ⁱ	2.7184 (3)	Mo1—S2ⁱⁱⁱ	2.4896 (8)
Mo1—Mo1ⁱⁱ	2.7515 (3)	Mo1—S2ⁱⁱ	2.4933 (6)
Mo1—S1	2.4108 (7)	Mo1—S2^iv	2.4340 (8)

Symmetry codes: (i) −y, x−y, z; (ii) y, −x+y, −z−1; (iii) −y−1/3, x−y−2/3, z+1/3; (iv) x−y, x, −z−1.

Acknowledgements

Intensity data were collected on the Nonius KappaCCD X-ray diffactometer system of the Centre de diffractométrie de l'Université de Rennes I (www.cdifx.univ-rennes1.fr).

References

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