The structure and crystal chemistry of vernadite in ferromanganese crusts

Lee, S.; Xu, H.; Xu, W.; Sun, X.

doi:10.1107/S2052520619006528

The structure and crystal chemistry of vernadite in ferromanganese crusts

The structure and crystal chemistry of vernadite in ferromanganese crusts from the Magellan Seamount in the north-west Pacific Ocean have been investigated using synchrotron X-ray diffraction (XRD), X-ray pair distribution function (PDF) and high-resolution transmission electron microscopy (TEM). XRD patterns of vernadite mainly show two strong diffraction peaks at 2.42–2.43 Å and 1.41 Å without or with a broad (001) diffraction peak, indicating thin layer nanophases along the c-direction. TEM images show flat and curved sheet-like nanocrystals with (001) layer thickness of ∼7.2 Å and ∼9.6 Å, and their interstratified structure. PDF patterns of the vernadite are similar to those from synthetic δ-MnO₂ and defective birnessite, suggesting a phyllomanganate framework. Combined XRD/PDF patterns suggest that vernadite in the outer part is associated with a higher density interlayer species at triple-edge sharing sites. The proportion of the 10 Å phase increases from the outer (young) part to the inner (old) part of the Mn crusts due to aging and sorption of Mn, Co and Ni from ambient seawater. This study suggests that this combined method of synchrotron radiation XRD/PDF and high-resolution TEM is a powerful tool to determine atomic structures of poorly crystallized nano-minerals. The mixture model of vernadite structure will help to understand the partitioning and distribution of trace elements in the ferromanganese crusts.

Keywords: vernadite; ferromanganese crusts; XRD; TEM; pair distribution function; mixed layer.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S2052520619006528/dk5073sup1.cif Contains datablocks global, 7A-vernadite, 10A-vernadite, mixed-vernadite_paper
	Portable Document Format (PDF) file https://doi.org/10.1107/S2052520619006528/dk5073sup2.pdf Supplementary material

CCDC references: 1914750; 1914751; 1914752

Computing details top

(7A-vernadite) top

Crystal data top

Ca0.06Mg0.06Mn1.12O2.32	c = 7.20 (2) Å
Monoclinic, C2/m	β = 97.3 (2)°
a = 4.952 (6) Å	T = 298 K
b = 2.833 (4) Å

Data collection top

Radiation source: Synchrotron	k = →
θ_max = 14.1°, θ_min = 0.8°	l = →
h = →

Refinement top

32 parameters

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

	x	y	z	U_iso*/U_eq	Occ. (<1)
K	0.5970	0.0000	0.5000	0.0240	0.0400
K	0.5970	0.0000	0.5000	0.0240	0.0400
Mn	0.0000	0.0000	0.0000		0.9100
MnIL	0.6721	0.0000	0.3160	0.0250	0.0900
OIL	0.0000	0.0000	0.5000	0.0290	0.1500
O	0.3620	0.0000	0.1330

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Mn	0.0040	0.0040	0.0140	0.0000	0.0000	0.0000
O	0.0090	0.0090	0.0250	0.0000	0.0000	0.0000

(10A-vernadite) top

Crystal data top

Monoclinic, C2/m	c = 9.60 (4) Å
a = 4.952 (6) Å	β = 99.0 (3)°
b = 2.833 (4) Å

Data collection top

h = →	l = →
k = →

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

	x	y	z	U_iso*/U_eq	Occ. (<1)
Mn	0.0000	0.0000	0.0000		0.8800
MnIL	0.0750	0.0000	0.2530	0.0330	0.1200
MnIL	0.0750	0.0000	0.2530	0.0330	0.0300
MnIL	0.0750	0.0000	0.2530	0.0330	0.0300
O	0.3660	0.0000	0.1010
O	0.2060	0.0000	0.5950	0.0250	0.1600

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Mn	0.0120	0.0120	0.0180	0.0000	0.0000	0.0000
O	0.0200	0.0200	0.0250	0.0000	0.0000	0.0000

(mixed-vernadite_paper) top

Crystal data top

Triclinic, P1	α = 90.0000 (1)°
a = 10.348 (5) Å	β = 103.18 (6)°
b = 5.70 (2) Å	γ = 90.0000 (1)°
c = 16.80 (5) Å

Data collection top

h = →	l = →
k = →

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

	x	y	z	U_iso*/U_eq	Occ. (<1)
Na	−0.2975	0.5000	0.2142	0.0020	0.0400
Na	−0.2975	0.5000	0.2142	0.0020	0.0400
Na	0.2975	0.5000	0.2142	0.0020	0.0400
Na	0.2975	0.5000	0.2142	0.0020	0.0400
Na	0.7975	0.0000	0.2142	0.0020	0.0400
Na	0.7975	0.0000	0.2142	0.0020	0.0400
Na	−0.2975	0.0000	0.2142	0.0020	0.0400
Na	−0.2975	0.0000	0.2142	0.0020	0.0400
Na	0.0475	0.2500	0.2142	0.0020	0.0400
Na	0.0475	0.2500	0.2142	0.0020	0.0400
Mg	0.1282	0.2500	0.5671	0.0130	0.1200
Mg	0.1282	0.2500	0.5671	0.0130	0.0300
Mg	0.1282	0.2500	0.5671	0.0130	0.0300
Mg	0.8782	0.5000	0.5671	0.0130	0.1200
Mg	0.8782	0.5000	0.5671	0.0130	0.0300
Mg	0.8782	0.5000	0.5671	0.0130	0.0300
Mg	0.3782	0.5000	0.5671	0.0130	0.1200
Mg	0.3782	0.5000	0.5671	0.0130	0.0300
Mg	0.3782	0.5000	0.5671	0.0130	0.0300
Mg	0.4481	0.0000	0.8613	0.0130	0.1200
Mg	0.4481	0.0000	0.8613	0.0130	0.0300
Mg	0.4481	0.0000	0.8613	0.0130	0.0300
Mg	0.1981	0.7500	0.8613	0.0130	0.1200
Mg	0.1981	0.7500	0.8613	0.0130	0.0300
Mg	0.1981	0.7500	0.8613	0.0130	0.0300
Mg	0.9481	0.5000	0.8613	0.0130	0.1200
Mg	0.9481	0.5000	0.8613	0.0130	0.0300
Mg	0.9481	0.5000	0.8613	0.0130	0.0300
Mg	0.4481	0.5000	0.8613	0.0130	0.1200
Mg	0.4481	0.5000	0.8613	0.0130	0.0300
Mg	0.4481	0.5000	0.8613	0.0130	0.0300
Mg	0.9481	0.0000	0.8613	0.0130	0.1200
Mg	0.9481	0.0000	0.8613	0.0130	0.0300
Mg	0.9481	0.0000	0.8613	0.0130	0.0300
Mg	0.1981	0.2500	0.8613	0.0130	0.1200
Mg	0.1981	0.2500	0.8613	0.0130	0.0300
Mg	0.1981	0.2500	0.8613	0.0130	0.0300
Mg	0.6981	0.7500	0.8613	0.0130	0.1200
Mg	0.6981	0.7500	0.8613	0.0130	0.0300
Mg	0.6981	0.7500	0.8613	0.0130	0.0300
Mg	0.6282	0.2500	0.5671	0.0130	0.1200
Mg	0.6282	0.2500	0.5671	0.0130	0.0300
Mg	0.6282	0.2500	0.5671	0.0130	0.0300
Mg	0.3782	0.0000	0.5671	0.0130	0.1200
Mg	0.3782	0.0000	0.5671	0.0130	0.0300
Mg	0.3782	0.0000	0.5671	0.0130	0.0300
Mg	0.8782	0.0000	0.5671	0.0130	0.1200
Mg	0.8782	0.0000	0.5671	0.0130	0.0300
Mg	0.8782	0.0000	0.5671	0.0130	0.0300
Mg	0.6282	0.7500	0.5671	0.0130	0.1200
Mg	0.6282	0.7500	0.5671	0.0130	0.0300
Mg	0.6282	0.7500	0.5671	0.0130	0.0300
Mg	0.1282	0.7500	0.5671	0.0130	0.1200
Mg	0.1282	0.7500	0.5671	0.0130	0.0300
Mg	0.1282	0.7500	0.5671	0.0130	0.0300
Mg	0.6981	0.2500	0.8613	0.0130	0.1200
Mg	0.6981	0.2500	0.8613	0.0130	0.0300
Mg	0.6981	0.2500	0.8613	0.0130	0.0300
Mn	0.2500	0.2500	0.0000	0.0050	0.9100
Mn	0.7500	0.2500	0.0000	0.0050	0.9100
Mn	0.7500	0.7500	0.4285	0.0050	0.9100
Mn	0.0000	0.0000	0.4285	0.0050	0.9100
Mn	0.0000	0.5000	0.4285	0.0050	0.9100
Mn	0.5000	0.0000	0.4285	0.0050	0.9100
Mn	0.5000	0.5000	0.4285	0.0050	0.9100
Mn	0.5000	0.0000	0.0000	0.0050	0.9100
Mn	0.0000	0.0000	0.0000	0.0050	0.9100
Mn	0.2500	0.7500	0.4285	0.0050	0.9100
Mn	0.7500	0.7500	0.0000	0.0050	0.9100
Mn	0.2500	0.2500	0.4285	0.0050	0.9100
Mn	0.7500	0.2500	0.4285	0.0050	0.9100
Mn	0.5000	0.5000	0.0000	0.0050	0.9100
Mn	0.2500	0.7500	0.0000	0.0050	0.9100
Mn	0.0000	0.5000	0.0000	0.0050	0.9100
MnIL	0.8490	0.2500	0.1340	1.0000	0.0900
MnIL	0.0990	0.5000	0.1340	1.0000	0.0900
MnIL	0.5990	0.0000	0.1340	1.0000	0.0900
MnIL	0.0990	0.0000	0.1340	1.0000	0.0900
MnIL	0.3490	0.2500	0.1340	1.0000	0.0900
MnIL	0.8490	0.7500	0.1340	1.0000	0.0900
MnIL	0.3490	0.7500	0.1340	1.0000	0.0900
MnIL	0.5990	0.5000	0.1340	1.0000	0.0900
MnO2	0.6500	0.0000	0.2943	1.0000	0.0900
MnO2	0.4000	0.2500	0.2943	1.0000	0.0900
MnO2	0.9000	0.2500	0.2943	1.0000	0.0900
MnO2	0.6500	0.5000	0.2943	1.0000	0.0900
MnO2	0.1500	0.0000	0.2943	1.0000	0.0900
MnO2	0.4000	0.7500	0.2943	1.0000	0.0900
MnO2	0.1500	0.5000	0.2943	1.0000	0.0900
MnO2	0.9000	0.7500	0.2943	1.0000	0.0900
Na	0.5475	0.7500	0.2142	0.0020	0.0400
Na	0.5475	0.7500	0.2142	0.0020	0.0400
Na	0.0475	0.7500	0.2142	0.0020	0.0400
Na	0.0475	0.7500	0.2142	0.0020	0.0400
Na	0.2025	0.5000	0.2142	0.0020	0.0400
Na	0.2025	0.5000	0.2142	0.0020	0.0400
Na	−0.0475	0.2500	0.2142	0.0020	0.0400
Na	−0.0475	0.2500	0.2142	0.0020	0.0400
Na	0.2975	0.0000	0.2142	0.0020	0.0400
Na	0.2975	0.0000	0.2142	0.0020	0.0400
Na	−0.0475	0.7500	0.2142	0.0020	0.0400
Na	−0.0475	0.7500	0.2142	0.0020	0.0400
Na	0.2025	0.0000	0.2142	0.0020	0.0400
Na	0.2025	0.0000	0.2142	0.0020	0.0400
Na	0.4525	0.7500	0.2142	0.0020	0.0400
Na	0.4525	0.7500	0.2142	0.0020	0.0400
Na	0.7975	0.5000	0.2142	0.0020	0.0400
Na	0.7975	0.5000	0.2142	0.0020	0.0400
Na	0.5475	0.2500	0.2142	0.0020	0.0400
Na	0.5475	0.2500	0.2142	0.0020	0.0400
Na	0.4525	0.2500	0.2142	0.0020	0.0400
Na	0.4525	0.2500	0.2142	0.0020	0.0400
O	0.0000	0.5000	0.2142	0.0170	0.1500
O	0.3300	0.2500	0.7764	0.0110	0.1500
O	0.8300	0.2500	0.7764	0.0110	0.1500
O	0.0800	0.5000	0.7764	0.0110	0.1500
O	0.8300	0.7500	0.7764	0.0110	0.1500
O	0.5800	0.0000	0.7764	0.0110	0.1500
O	0.5800	0.5000	0.7764	0.0110	0.1500
O	0.7500	0.2500	0.2142	0.0170	0.1500
O	0.3300	0.7500	0.7764	0.0110	0.1500
O	0.0727	0.5000	0.6520	0.0110	0.1500
O	0.5727	0.0000	0.6520	0.0110	0.1500
O	0.0727	0.0000	0.6520	0.0110	0.1500
O	0.3227	0.2500	0.6520	0.0110	0.1500
O	0.8227	0.2500	0.6520	0.0110	0.1500
O	0.8227	0.7500	0.6520	0.0110	0.1500
O	0.3227	0.7500	0.6520	0.0110	0.1500
O	0.0000	0.0000	0.2142	0.0170	0.1500
O	0.2500	0.2500	0.2142	0.0170	0.1500
O	0.5000	0.5000	0.2142	0.0170	0.1500
O	0.7500	0.7500	0.2142	0.0170	0.1500
O	0.0800	0.0000	0.7764	0.0110	0.1500
O	0.2500	0.7500	0.2142	0.0170	0.1500
O	0.5000	0.0000	0.2142	0.0170	0.1500
O	0.5727	0.5000	0.6520	0.0110	0.1500
O1	0.1835	0.0000	0.0538	0.0110
O1	0.1837	0.0000	0.4823	0.0110
O1	0.6837	0.0000	0.4823	0.0110
O1	0.1837	0.5000	0.4823	0.0110
O1	0.9337	0.2500	0.4823	0.0110
O1	0.4337	0.2500	0.4823	0.0110
O1	0.6837	0.5000	0.4823	0.0110
O1	0.4337	0.7500	0.4823	0.0110
O1	0.9337	0.7500	0.4823	0.0110
O1	0.0667	0.7500	0.3747	0.0110
O1	0.3167	0.5000	0.3747	0.0110
O1	0.8167	0.5000	0.3747	0.0110
O1	0.0667	0.2500	0.3747	0.0110
O1	0.3167	0.0000	0.3747	0.0110
O1	0.5667	0.2500	0.3747	0.0110
O1	0.8167	0.0000	0.3747	0.0110
O1	0.9335	0.2500	0.0538	0.0110
O1	0.6835	0.0000	0.0538	0.0110
O1	0.4335	0.2500	0.0538	0.0110
O1	0.1835	0.5000	0.0538	0.0110
O1	0.6835	0.5000	0.0538	0.0110
O1	0.9335	0.7500	0.0538	0.0110
O1	0.4335	0.7500	0.0538	0.0110
O1	0.5667	0.7500	0.3747	0.0110
O1	0.5665	0.7500	0.9462	0.0110
O1	0.5665	0.2500	0.9462	0.0110
O1	0.8165	0.0000	0.9462	0.0110
O1	0.3165	0.5000	0.9462	0.0110
O1	0.3165	0.0000	0.9462	0.0110
O1	0.0665	0.7500	0.9462	0.0110
O1	0.8165	0.5000	0.9462	0.0110
O1	0.0665	0.2500	0.9462	0.0110

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