Structural and enhanced hydrogen storage properties of the Li12Mg3Si3Al phase

Pavlyuk, V.; Ciesielski, W.; Kulawik, D.; Pavlyuk, N.; Dmytriv, G.

doi:10.1107/S2053229621004113

Structural and enhanced hydrogen storage properties of the Li₁₂Mg₃Si₃Al phase

V. Pavlyuk, W. Ciesielski, D. Kulawik, N. Pavlyuk and G. Dmytriv

The multicomponent alumosilicide Li₁₂Mg₃Si₃Al (cubic, space group I $\overline{4}$ 3d, cI76) belongs to the structural family based on the Cu₁₅Si₄ type. The Li atoms are ordered and occupy the site with symmetry 1 and the Mg atoms occupy the site with $\overline{4}$ .. symmetry. The Si/Al statistical mixture occupies the site with .3. symmetry. The coordination polyhedra around the Li atoms are 13-vertex distorted pseudo-Frank–Kasper polyhedra. The environments of the Mg and Si/Al atoms are icosahedral. The hydrogen storage characteristics of Li₁₂Mg₃Si₃Al were investigated. The reversible hydrogen storage capacity of the title compound is excellent and the gravimetric storage capacity of this new material, corresponding to 9.1 wt% H₂, is higher compared to Li₁₂Mg₃Si₄ (8.8 wt%). The enthalpy of hydrogen desorption is 86 kJ mol⁻¹ and is lower compared to known lithium-based hydrides.

Keywords: hydrogenation; hydrogen storage material; lithium and magnesium alloy; intermetallic; crystal structure; quaternary alloy.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S2053229621004113/yo3079sup1.cif Contains datablocks I, global
	Structure factor file (CIF format) https://doi.org/10.1107/S2053229621004113/yo3079Isup2.hkl Contains datablock I

CCDC reference: 2078493

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis CCD (Oxford Diffraction, 2008); data reduction: CrysAlis RED (Oxford Diffraction, 2008); program(s) used to solve structure: SHELXS2014 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015).

Dodecalithium trimagnesium trisilicon aluminium top

Crystal data top

Li₁₂Mg₃Si₃Al	Mo Kα radiation, λ = 0.71073 Å
M_r = 89.16	Cell parameters from 217 reflections
Cubic, I43d	θ = 4.7–25.2°
a = 10.7338 (9) Å	µ = 0.54 mm⁻¹
V = 1236.7 (3) Å³	T = 293 K
Z = 12	Prism, metallic grey
F(000) = 508	0.05 × 0.03 × 0.02 mm
D_x = 1.437 Mg m⁻³ D_m = 1.45 (3) Mg m⁻³ D_m measured by volumetric

Data collection top

Oxford Diffraction Xcalibur3 CCD diffractometer	217 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.056
ω scans	θ_max = 27.2°, θ_min = 4.7°
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2008)	h = −13→13
T_min = 0.945, T_max = 0.989	k = −13→13
2454 measured reflections	l = −13→13
230 independent reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	w = 1/[σ²(F_o²)] where P = (F_o² + 2F_c²)/3
R[F² > 2σ(F²)] = 0.018	(Δ/σ)_max = 0.002
wR(F²) = 0.035	Δρ_max = 0.20 e Å⁻³
S = 1.02	Δρ_min = −0.10 e Å⁻³
230 reflections	Absolute structure: Flack x determined using 87 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
16 parameters	Absolute structure parameter: 0.7 (2)

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. The structure of the title phase was solved by direct methods by means SHELXS2014/7 package program (Sheldrick, 2008). The structure refinements was conducted by means SHELXL2014/7 (Sheldrick, 2015).

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

	x	y	z	U_iso*/U_eq	Occ. (<1)
Si	0.21048 (5)	0.21048 (5)	0.21048 (5)	0.0489 (2)	0.7525
Al	0.21048 (5)	0.21048 (5)	0.21048 (5)	0.0489 (2)	0.2475
Mg	0.3750	0.0000	0.2500	0.0507 (3)
Li	0.0450 (3)	0.3867 (3)	0.1482 (3)	0.0512 (7)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Si	0.0489 (2)	0.0489 (2)	0.0489 (2)	0.0000 (2)	0.0000 (2)	0.0000 (2)
Al	0.0489 (2)	0.0489 (2)	0.0489 (2)	0.0000 (2)	0.0000 (2)	0.0000 (2)
Mg	0.0511 (7)	0.0504 (5)	0.0504 (5)	0.000	0.000	0.000
Li	0.0507 (16)	0.0534 (16)	0.0495 (17)	0.0000 (12)	−0.0016 (13)	0.0007 (14)

Geometric parameters (Å, º) top

Si—Liⁱ	2.599 (3)	Mg—Li^xi	2.883 (3)
Si—Liⁱⁱ	2.599 (3)	Mg—Li^xii	2.883 (3)
Si—Liⁱⁱⁱ	2.599 (3)	Mg—Li^v	2.883 (3)
Si—Li	2.679 (3)	Mg—Alⁱ	2.8987 (2)
Si—Li^iv	2.679 (3)	Mg—Siⁱ	2.8987 (2)
Si—Li^v	2.679 (3)	Mg—Al^xiii	2.8987 (2)
Si—Mg	2.8987 (2)	Mg—Si^xiii	2.8987 (2)
Si—Mg^iv	2.8987 (2)	Li—Al^xiv	2.599 (3)
Si—Mg^v	2.8987 (2)	Li—Si^xiv	2.599 (3)
Si—Li^vi	3.009 (3)	Li—Li^xv	2.707 (5)
Si—Li^vii	3.009 (3)	Li—Li^xvi	2.707 (5)
Si—Li^viii	3.009 (3)	Li—Mg^v	2.718 (3)
Mg—Li^ix	2.718 (3)	Li—Li^xvii	2.880 (5)
Mg—Liⁱ	2.718 (3)	Li—Liⁱⁱⁱ	2.880 (5)
Mg—Li^x	2.718 (3)	Li—Mg^iv	2.883 (3)
Mg—Li^iv	2.718 (3)	Li—Al^vi	3.009 (3)
Mg—Li^vii	2.883 (3)	Li—Si^vi	3.009 (3)

Liⁱ—Si—Liⁱⁱ	62.77 (11)	Li^ix—Mg—Alⁱ	127.07 (6)
Liⁱ—Si—Liⁱⁱⁱ	62.77 (11)	Liⁱ—Mg—Alⁱ	56.87 (6)
Liⁱⁱ—Si—Liⁱⁱⁱ	62.77 (11)	Li^x—Mg—Alⁱ	55.02 (6)
Liⁱ—Si—Li	128.88 (11)	Li^iv—Mg—Alⁱ	121.14 (6)
Liⁱⁱ—Si—Li	93.60 (9)	Li^vii—Mg—Alⁱ	159.32 (6)
Liⁱⁱⁱ—Si—Li	66.11 (11)	Li^xi—Mg—Alⁱ	62.72 (6)
Liⁱ—Si—Li^iv	93.60 (9)	Li^xii—Mg—Alⁱ	55.21 (6)
Liⁱⁱ—Si—Li^iv	66.11 (11)	Li^v—Mg—Alⁱ	95.35 (6)
Liⁱⁱⁱ—Si—Li^iv	128.88 (11)	Li^ix—Mg—Siⁱ	127.07 (6)
Li—Si—Li^iv	118.60 (2)	Liⁱ—Mg—Siⁱ	56.87 (6)
Liⁱ—Si—Li^v	66.11 (11)	Li^x—Mg—Siⁱ	55.02 (6)
Liⁱⁱ—Si—Li^v	128.88 (11)	Li^iv—Mg—Siⁱ	121.14 (6)
Liⁱⁱⁱ—Si—Li^v	93.60 (9)	Li^vii—Mg—Siⁱ	159.32 (6)
Li—Si—Li^v	118.60 (2)	Li^xi—Mg—Siⁱ	62.72 (6)
Li^iv—Si—Li^v	118.60 (2)	Li^xii—Mg—Siⁱ	55.21 (6)
Liⁱ—Si—Mg	58.96 (7)	Li^v—Mg—Siⁱ	95.35 (6)
Liⁱⁱ—Si—Mg	91.31 (7)	Alⁱ—Mg—Siⁱ	0.0
Liⁱⁱⁱ—Si—Mg	121.71 (7)	Li^ix—Mg—Al^xiii	55.02 (6)
Li—Si—Mg	172.12 (7)	Liⁱ—Mg—Al^xiii	121.14 (6)
Li^iv—Si—Mg	58.17 (7)	Li^x—Mg—Al^xiii	56.87 (6)
Li^v—Si—Mg	62.09 (7)	Li^iv—Mg—Al^xiii	127.07 (6)
Liⁱ—Si—Mg^iv	91.31 (7)	Li^vii—Mg—Al^xiii	55.21 (6)
Liⁱⁱ—Si—Mg^iv	121.71 (7)	Li^xi—Mg—Al^xiii	159.32 (6)
Liⁱⁱⁱ—Si—Mg^iv	58.96 (7)	Li^xii—Mg—Al^xiii	95.35 (6)
Li—Si—Mg^iv	62.09 (7)	Li^v—Mg—Al^xiii	62.72 (6)
Li^iv—Si—Mg^iv	172.12 (7)	Alⁱ—Mg—Al^xiii	111.787 (14)
Li^v—Si—Mg^iv	58.17 (7)	Siⁱ—Mg—Al^xiii	111.787 (14)
Mg—Si—Mg^iv	119.981 (1)	Li^ix—Mg—Si^xiii	55.02 (6)
Liⁱ—Si—Mg^v	121.71 (7)	Liⁱ—Mg—Si^xiii	121.14 (6)
Liⁱⁱ—Si—Mg^v	58.96 (7)	Li^x—Mg—Si^xiii	56.87 (6)
Liⁱⁱⁱ—Si—Mg^v	91.31 (7)	Li^iv—Mg—Si^xiii	127.07 (6)
Li—Si—Mg^v	58.17 (7)	Li^vii—Mg—Si^xiii	55.21 (6)
Li^iv—Si—Mg^v	62.09 (7)	Li^xi—Mg—Si^xiii	159.32 (6)
Li^v—Si—Mg^v	172.12 (7)	Li^xii—Mg—Si^xiii	95.35 (6)
Mg—Si—Mg^v	119.981 (1)	Li^v—Mg—Si^xiii	62.72 (6)
Mg^iv—Si—Mg^v	119.981 (1)	Alⁱ—Mg—Si^xiii	111.8
Liⁱ—Si—Li^vi	137.69 (11)	Siⁱ—Mg—Si^xiii	111.787 (14)
Liⁱⁱ—Si—Li^vi	156.97 (12)	Al^xiii—Mg—Si^xiii	0.0
Liⁱⁱⁱ—Si—Li^vi	112.85 (10)	Al^xiv—Li—Si^xiv	0.0
Li—Si—Li^vi	65.49 (10)	Al^xiv—Li—Si	130.8
Li^iv—Si—Li^vi	114.19 (9)	Si^xiv—Li—Si	130.84 (13)
Li^v—Si—Li^vi	72.53 (2)	Al^xiv—Li—Li^xv	58.61 (6)
Mg—Si—Li^vi	108.52 (6)	Si^xiv—Li—Li^xv	58.61 (6)
Mg^iv—Si—Li^vi	58.38 (6)	Si—Li—Li^xv	120.63 (16)
Mg^v—Si—Li^vi	99.87 (6)	Al^xiv—Li—Li^xvi	58.61 (6)
Liⁱ—Si—Li^vii	112.85 (10)	Si^xiv—Li—Li^xvi	58.61 (6)
Liⁱⁱ—Si—Li^vii	137.69 (11)	Si—Li—Li^xvi	170.22 (7)
Liⁱⁱⁱ—Si—Li^vii	156.97 (12)	Li^xv—Li—Li^xvi	60.0
Li—Si—Li^vii	114.19 (9)	Al^xiv—Li—Mg^v	66.02 (8)
Li^iv—Si—Li^vii	72.525 (19)	Si^xiv—Li—Mg^v	66.02 (8)
Li^v—Si—Li^vii	65.49 (10)	Si—Li—Mg^v	64.96 (7)
Mg—Si—Li^vii	58.38 (6)	Li^xv—Li—Mg^v	93.06 (11)
Mg^iv—Si—Li^vii	99.87 (6)	Li^xvi—Li—Mg^v	124.62 (6)
Mg^v—Si—Li^vii	108.52 (6)	Al^xiv—Li—Li^xvii	58.28 (10)
Li^vi—Si—Li^vii	53.47 (9)	Si^xiv—Li—Li^xvii	58.28 (10)
Liⁱ—Si—Li^viii	156.97 (12)	Si—Li—Li^xvii	100.45 (15)
Liⁱⁱ—Si—Li^viii	112.85 (10)	Li^xv—Li—Li^xvii	116.89 (11)
Liⁱⁱⁱ—Si—Li^viii	137.69 (11)	Li^xvi—Li—Li^xvii	87.00 (16)
Li—Si—Li^viii	72.525 (19)	Mg^v—Li—Li^xvii	61.91 (13)
Li^iv—Si—Li^viii	65.49 (10)	Al^xiv—Li—Liⁱⁱⁱ	127.44 (13)
Li^v—Si—Li^viii	114.19 (9)	Si^xiv—Li—Liⁱⁱⁱ	127.44 (13)
Mg—Si—Li^viii	99.87 (6)	Si—Li—Liⁱⁱⁱ	55.61 (11)
Mg^iv—Si—Li^viii	108.52 (6)	Li^xv—Li—Liⁱⁱⁱ	173.89 (9)
Mg^v—Si—Li^viii	58.38 (6)	Li^xvi—Li—Liⁱⁱⁱ	122.74 (18)
Li^vi—Si—Li^viii	53.47 (9)	Mg^v—Li—Liⁱⁱⁱ	89.34 (14)
Li^vii—Si—Li^viii	53.47 (9)	Li^xvii—Li—Liⁱⁱⁱ	69.17 (12)
Li^ix—Mg—Liⁱ	174.71 (12)	Al^xiv—Li—Mg^iv	166.42 (14)
Li^ix—Mg—Li^x	90.122 (6)	Si^xiv—Li—Mg^iv	166.42 (14)
Liⁱ—Mg—Li^x	90.122 (6)	Si—Li—Mg^iv	62.69 (6)
Li^ix—Mg—Li^iv	90.122 (6)	Li^xv—Li—Mg^iv	118.11 (6)
Liⁱ—Mg—Li^iv	90.122 (6)	Li^xvi—Li—Mg^iv	107.93 (10)
Li^x—Mg—Li^iv	174.71 (12)	Mg^v—Li—Mg^iv	127.33 (11)
Li^ix—Mg—Li^vii	61.80 (10)	Li^xvii—Li—Mg^iv	122.97 (10)
Liⁱ—Mg—Li^vii	113.24 (8)	Liⁱⁱⁱ—Li—Mg^iv	56.29 (10)
Li^x—Mg—Li^vii	110.66 (11)	Al^xiv—Li—Al^vi	111.73 (10)
Li^iv—Mg—Li^vii	74.04 (6)	Si^xiv—Li—Al^vi	111.73 (10)
Li^ix—Mg—Li^xi	110.66 (11)	Si—Li—Al^vi	107.7
Liⁱ—Mg—Li^xi	74.04 (6)	Li^xv—Li—Al^vi	63.26 (5)
Li^x—Mg—Li^xi	113.24 (8)	Li^xvi—Li—Al^vi	63.26 (5)
Li^iv—Mg—Li^xi	61.80 (10)	Mg^v—Li—Al^vi	148.40 (11)
Li^vii—Mg—Li^xi	135.47 (7)	Li^xvii—Li—Al^vi	146.18 (16)
Li^ix—Mg—Li^xii	74.04 (6)	Liⁱⁱⁱ—Li—Al^vi	112.35 (14)
Liⁱ—Mg—Li^xii	110.66 (11)	Mg^iv—Li—Al^vi	58.89 (6)
Li^x—Mg—Li^xii	61.80 (10)	Al^xiv—Li—Si^vi	111.7
Li^iv—Mg—Li^xii	113.24 (8)	Si^xiv—Li—Si^vi	111.73 (10)
Li^vii—Mg—Li^xii	135.47 (7)	Si—Li—Si^vi	107.70 (10)
Li^xi—Mg—Li^xii	64.80 (11)	Li^xv—Li—Si^vi	63.26 (5)
Li^ix—Mg—Li^v	113.24 (8)	Li^xvi—Li—Si^vi	63.26 (5)
Liⁱ—Mg—Li^v	61.80 (10)	Mg^v—Li—Si^vi	148.40 (11)
Li^x—Mg—Li^v	74.04 (6)	Li^xvii—Li—Si^vi	146.18 (16)
Li^iv—Mg—Li^v	110.66 (11)	Liⁱⁱⁱ—Li—Si^vi	112.35 (14)
Li^vii—Mg—Li^v	64.80 (11)	Mg^iv—Li—Si^vi	58.89 (6)
Li^xi—Mg—Li^v	135.47 (7)	Al^vi—Li—Si^vi	0.0
Li^xii—Mg—Li^v	135.47 (7)

Symmetry codes: (i) −y+3/4, −x+1/4, z+1/4; (ii) z+1/4, −y+3/4, −x+1/4; (iii) −x+1/4, z+1/4, −y+3/4; (iv) y, z, x; (v) z, x, y; (vi) −x, −y+1/2, z; (vii) z, −x, −y+1/2; (viii) −y+1/2, z, −x; (ix) −y+3/4, x−1/4, −z+1/4; (x) y, −z, −x+1/2; (xi) −z+3/4, y−1/4, −x+1/4; (xii) −z+3/4, −y+1/4, x+1/4; (xiii) x, −y, −z+1/2; (xiv) −y+1/4, −x+3/4, z−1/4; (xv) y−1/2, −z+1/2, −x; (xvi) −z, x+1/2, −y+1/2; (xvii) −x+1/4, −z+3/4, y−1/4.

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