Crystal chemistry of mimetite, Pb10(AsO4)6Cl1.48O0.26, and finnemanite, Pb10(AsO3)6Cl2

Baikie, T.; Ferraris, C.; Klooster, W.T.; Madhavi, S.; Pramana, S.S.; Pring, A.; Schmidt, G.; White, T.J.

doi:10.1107/S0108768107066402

Crystal chemistry of mimetite, Pb₁₀(AsO₄)₆Cl_1.48O_0.26, and finnemanite, Pb₁₀(AsO₃)₆Cl₂

T. Baikie, C. Ferraris, W. T. Klooster, S. Madhavi, S. S. Pramana, A. Pring, G. Schmidt and T. J. White

The crystal chemistries of synthetic mimetite, Pb₁₀(As⁵⁺O₄)₆(Cl_2 - xO_x/2), a neutral apatite, and finnemanite, Pb₁₀(As³⁺O₃)₆Cl₂, a reduced apatite, were characterized using a combination of X-ray powder diffraction, neutron diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Both phases conform to hexagonal P6₃/m symmetry; however, the temperature-driven transformation of clinomimetite to mimetite described earlier was not confirmed. The average mimetite structure is best described through the introduction of partially occupied oxygen sites. A better understanding of the mixed arsenic speciation in apatites can guide the formulation of waste form ceramics and improve models of long-term durability after landfill disposal.

Keywords: powder diffraction; transmission electron microscropy; photoelectron spectroscopy; ceramics.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768107066402/lm5013sup1.cif Contains datablocks global, As6Cl2O18Pb10, As6Cl1.48O24.26Pb10_298K, As6Cl1.48O24.26Pb10_373K, As6Cl1.48O24.26Pb10_423K, As6Cl1.48O24.26Pb10_473K
	Structure factor file (CIF format) https://doi.org/10.1107/S0108768107066402/lm5013As6Cl2O18Pb10sup2.hkl Contains datablock As6Cl2O18Pb10
	Structure factor file (CIF format) https://doi.org/10.1107/S0108768107066402/lm5013As6Cl1.48O24.26Pb10_298Ksup3.hkl Contains datablock As6Cl1.48O24.26Pb10_298K
	Structure factor file (CIF format) https://doi.org/10.1107/S0108768107066402/lm5013As6Cl1.48O24.26Pb10_373Ksup4.hkl Contains datablock As6Cl1.48O24.26Pb10_373K
	Structure factor file (CIF format) https://doi.org/10.1107/S0108768107066402/lm5013As6Cl1.48O24.26Pb10_423Ksup5.hkl Contains datablock As6Cl1.48O24.26Pb10_423K
	Structure factor file (CIF format) https://doi.org/10.1107/S0108768107066402/lm5013As6Cl1.48O24.26Pb10_473Ksup6.hkl Contains datablock As6Cl1.48O24.26Pb10_473K
	Portable Document Format (PDF) file https://doi.org/10.1107/S0108768107066402/lm5013sup7.pdf Supplementary material
	Rietveld powder data file (CIF format) https://doi.org/10.1107/S0108768107066402/lm5013As6Cl1.48O24.26Pb10_298Ksup8.rtv Contains datablock As6Cl1.48O24.26Pb10_298K
	Rietveld powder data file (CIF format) https://doi.org/10.1107/S0108768107066402/lm5013As6Cl1.48O24.26Pb10_373Ksup9.rtv Contains datablock As6Cl1.48O24.26Pb10_373K
	Rietveld powder data file (CIF format) https://doi.org/10.1107/S0108768107066402/lm5013As6Cl1.48O24.26Pb10_423Ksup10.rtv Supplementary material
	Rietveld powder data file (CIF format) https://doi.org/10.1107/S0108768107066402/lm5013As6Cl1.48O24.26Pb10_473Ksup11.rtv Supplementary material

Computing details top

Data collection: local for As6Cl2O18Pb10; Shimadzu XRD 6000 for As6Cl1.48O24.26Pb10_298K, As6Cl1.48O24.26Pb10_373K, As6Cl1.48O24.26Pb10_423K, As6Cl1.48O24.26Pb10_473K. For all compounds, cell refinement: TOPAS (Bruker, 2005); data reduction: TOPAS (Bruker, 2005); program(s) used to solve structure: TOPAS (Bruker, 2005); program(s) used to refine structure: TOPAS (Bruker, 2005); molecular graphics: ATOMS (Shape, 2004), GFOURIER (Gonzales-Platas, J. & Rodriguez-Carvajal, J. (2006).

Figures top

(As6Cl2O18Pb10) top

Crystal data top

As6Cl2O18Pb₁₀	F(000) = 288.5
M_r = 2880.43	D_x = 7.369 Mg m⁻³
Hexagonal, P6₃/m	Neutron radiation, λ = 1.8834 Å
Hall symbol: -P 6c	T = 298 K
a = 10.2972 (6) Å	grey
c = 7.0690 (6) Å	cylinder, ? × ? × ? mm
V = 649.12 (8) Å³	Specimen preparation: Prepared at 323 K and 100 kPa
Z = 1

Data collection top

Local diffractometer	Data collection mode: reflection
Ge 115 monochromator	Scan method: Stationary detector
Specimen mounting: vanadium can with He exchange gas

Refinement top

Least-squares matrix: full	Excluded region(s): 0.027 to 10 degrees unreliable due to background
R_p = 0.060	Profile function: pseudo-Voigt
R_wp = 0.077	20 parameters
R_exp = 0.090	0 restraints
R_Bragg = 0.034	1 constraint
χ² = 0.740	Weighting scheme based on measured s.u.'s
3001 data points

Crystal data top

As6Cl2O18Pb₁₀	V = 649.12 (8) Å³
M_r = 2880.43	Z = 1
Hexagonal, P6₃/m	Neutron radiation, λ = 1.8834 Å
a = 10.2972 (6) Å	T = 298 K
c = 7.0690 (6) Å	cylinder, ? × ? × ? mm

Data collection top

Local diffractometer	Data collection mode: reflection
Specimen mounting: vanadium can with He exchange gas	Scan method: Stationary detector

Refinement top

R_p = 0.060	χ² = 0.740
R_wp = 0.077	3001 data points
R_exp = 0.090	20 parameters
R_Bragg = 0.034	0 restraints

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

	x	y	z	B_iso*/B_eq
Pb1	0.333333	0.666667	0.9937 (12)	1.0 (1)
Pb2	0.2644 (6)	0.0360 (7)	0.25	1.0 (1)
As1	0.4095 (11)	0.4032 (12)	0.25	1.2 (1)
O1	0.6076 (12)	0.4653 (12)	0.25	1.0 (1)
O2	0.3703 (8)	0.2789 (8)	0.0568 (9)	1.0 (1)
Cl	0	0	0	1.7 (1)

(As6Cl1.48O24.26Pb10_298K) top

Crystal data top

As6Cl1.48O24.26Pb₁₀	F(000) = 288.5
M_r = 2962.16	D_x = 7.322 Mg m⁻³
Hexagonal, P6₃/m	Neutron radiation, λ = 1.8834 Å
Hall symbol: -P 6c	T = 298 K
a = 10.2055 (2) Å	white
c = 7.4483 (2) Å	cylinder, ? × ? × ? mm
V = 671.83 (3) Å³	Specimen preparation: Prepared at 973 K and 100 kPa, cooled at 100 K min⁻¹
Z = 1

Data collection top

Local diffractometer	Data collection mode: reflection
Ge 115 monochromator	Scan method: Stationary detector
Specimen mounting: vanadium can with He exchange gas

Refinement top

Least-squares matrix: full	Excluded region(s): 0.027 to 10 degrees unreliable due to background
R_p = 0.046	Profile function: pseudo-Voigt
R_wp = 0.058	45 parameters
R_exp = 0.090	0 restraints
R_Bragg = 0.019	1 constraint
χ² = 0.423	Weighting scheme based on measured s.u.'s
3001 data points

Crystal data top

As6Cl1.48O24.26Pb₁₀	V = 671.83 (3) Å³
M_r = 2962.16	Z = 1
Hexagonal, P6₃/m	Neutron radiation, λ = 1.8834 Å
a = 10.2055 (2) Å	T = 298 K
c = 7.4483 (2) Å	cylinder, ? × ? × ? mm

Data collection top

Local diffractometer	Data collection mode: reflection
Specimen mounting: vanadium can with He exchange gas	Scan method: Stationary detector

Refinement top

R_p = 0.046	χ² = 0.423
R_wp = 0.058	3001 data points
R_exp = 0.090	45 parameters
R_Bragg = 0.019	0 restraints

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

	x	y	z	B_iso*/B_eq	Occ. (<1)
Pb1	0.333333	0.666667	0.0073 (4)	1.3 (1)
Pb2	0.2491 (2)	0.0027 (3)	0.25	1.4 (1)
As1	0.4060 (3)	0.3822 (3)	0.25	1.1 (1)
O1	0.3268 (4)	0.4932 (4)	0.25	1.7 (1)
O2	0.5965 (4)	0.4851 (5)	0.2193 (1)	1.9 (1)	0.5
O3a	0.3306 (6)	0.2444 (6)	0.0917 (6)	1.2 (1)	0.5
O3b	0.3847 (6)	0.2953 (6)	0.0501 (1)	1.6 (1)	0.5
O4	0	0	0.25	2.5 (2)	0.13
Cl1	0	0	0	1.5 (1)	0.74

(As6Cl1.48O24.26Pb10_373K) top

Crystal data top

As6Cl1.48O24.26Pb₁₀	F(000) = 288.5
M_r = 2962.16	D_x = 7.296 Mg m⁻³
Hexagonal, P6₃/m	Neutron radiation, λ = 1.8834 Å
Hall symbol: -P 6c	T = 373 K
a = 10.2224 (3) Å	white
c = 7.4494 (2) Å	cylinder, ? × ? × ? mm
V = 674.15 (3) Å³	Specimen preparation: Prepared at 973 K and 100 kPa, cooled at 100 K min⁻¹
Z = 1

Data collection top

Local diffractometer	Data collection mode: reflection
Ge 115 monochromator	Scan method: Stationary detector
Specimen mounting: vanadium can with He exchange gas

Refinement top

Least-squares matrix: full	Excluded region(s): 0.027 to 10 degrees unreliable due to background
R_p = 0.043	Profile function: pseudo-Voigt
R_wp = 0.055	48 parameters
R_exp = 0.088	0 restraints
R_Bragg = 0.017	1 constraint
χ² = 0.397	Weighting scheme based on measured s.u.'s
3001 data points

Crystal data top

As6Cl1.48O24.26Pb₁₀	V = 674.15 (3) Å³
M_r = 2962.16	Z = 1
Hexagonal, P6₃/m	Neutron radiation, λ = 1.8834 Å
a = 10.2224 (3) Å	T = 373 K
c = 7.4494 (2) Å	cylinder, ? × ? × ? mm

Data collection top

Local diffractometer	Data collection mode: reflection
Specimen mounting: vanadium can with He exchange gas	Scan method: Stationary detector

Refinement top

R_p = 0.043	χ² = 0.397
R_wp = 0.055	3001 data points
R_exp = 0.088	48 parameters
R_Bragg = 0.017	0 restraints

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

	x	y	z	B_iso*/B_eq	Occ. (<1)
Pb1	0.333333	0.666667	0.0049 (5)	2.0 (1)
Pb2	0.2497 (3)	0.0043 (4)	0.25	2.1 (1)
As1	0.4050 (4)	0.3809 (4)	0.25	0.9 (1)
O1	0.3282 (4)	0.4934 (4)	0.25	1.8 (1)
O2	0.5959 (5)	0.4833 (6)	0.2225 (12)	2.2 (1)	0.5
O3a	0.3310 (8)	0.2456 (8)	0.0890 (8)	1.4 (1)	0.5
O3b	0.3832 (7)	0.2923 (7)	0.0544 (7)	1.3 (1)	0.5
O4	0	0	0.25	2.4 (2)	0.13
Cl1	0	0	0	1.7 (1)	0.74

(As6Cl1.48O24.26Pb10_423K) top

Crystal data top

As6Cl1.48O24.26Pb₁₀	F(000) = 288.5
M_r = 2962.16	D_x = 7.278 Mg m⁻³
Hexagonal, P6₃/m	Neutron radiation, λ = 1.8834 Å
Hall symbol: -P 6c	T = 423 K
a = 10.2323 (3) Å	white
c = 7.4533 (2) Å	cylinder, ? × ? × ? mm
V = 675.82 (3) Å³	Specimen preparation: Prepared at 973 K and 100 kPa, cooled at 100 K min⁻¹
Z = 1

Data collection top

Local diffractometer	Data collection mode: reflection
Ge 115 monochromator	Scan method: Stationary detector
Specimen mounting: vanadium can with He exchange gas

Refinement top

Least-squares matrix: full	Excluded region(s): 0.027 to 10 degrees unreliable due to background
R_p = 0.045	Profile function: pseudo-Voigt
R_wp = 0.057	48 parameters
R_exp = 0.089	0 restraints
R_Bragg = 0.019	1 constraint
χ² = 0.423	Weighting scheme based on measured s.u.'s
3001 data points

Crystal data top

As6Cl1.48O24.26Pb₁₀	V = 675.82 (3) Å³
M_r = 2962.16	Z = 1
Hexagonal, P6₃/m	Neutron radiation, λ = 1.8834 Å
a = 10.2323 (3) Å	T = 423 K
c = 7.4533 (2) Å	cylinder, ? × ? × ? mm

Data collection top

Local diffractometer	Data collection mode: reflection
Specimen mounting: vanadium can with He exchange gas	Scan method: Stationary detector

Refinement top

R_p = 0.045	χ² = 0.423
R_wp = 0.057	3001 data points
R_exp = 0.089	48 parameters
R_Bragg = 0.019	0 restraints

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

	x	y	z	B_iso*/B_eq	Occ. (<1)
Pb1	0.333333	0.666667	0.0048 (6)	2.0 (1)
Pb2	0.2499 (3)	0.0041 (4)	0.25	2.3 (1)
As1	0.4048 (4)	0.3806 (4)	0.25	1.1 (1)
O1	0.3283 (5)	0.4924 (5)	0.25	2.0 (1)
O2	0.5965 (5)	0.4825 (6)	0.2214 (12)	2.0 (2)	0.5
O3a	0.3344 (9)	0.2484 (9)	0.0906 (9)	1.6 (2)	0.5
O3b	0.3910 (8)	0.2907 (8)	0.0532 (8)	1.8 (2)	0.5
O4	0	0	0.25	2.4 (2)	0.13
Cl1	0	0	0	2.0 (1)	0.74

(As6Cl1.48O24.26Pb10_473K) top

Crystal data top

As6Cl1.48O24.26Pb₁₀	F(000) = 288.5
M_r = 2962.16	D_x = 7.259 Mg m⁻³
Hexagonal, P6₃/m	Neutron radiation, λ = 1.8834 Å
Hall symbol: -P 6c	T = 473 K
a = 10.2415 (3) Å	white
c = 7.4594 (2) Å	cylinder, ? × ? × ? mm
V = 677.59 (3) Å³	Specimen preparation: Prepared at 973 K and 100 kPa, cooled at 100 K min⁻¹
Z = 1

Data collection top

Local diffractometer	Data collection mode: reflection
Ge 115 monochromator	Scan method: Stationary detector
Specimen mounting: vanadium can with He exchange gas

Refinement top

Least-squares matrix: full	Excluded region(s): 0.027 to 10 degrees unreliable due to background
R_p = 0.049	Profile function: pseudo-Voigt
R_wp = 0.062	48 parameters
R_exp = 0.011	0 restraints
R_Bragg = 0.019	1 constraint
χ² = 0.336	Weighting scheme based on measured s.u.'s
3001 data points

Crystal data top

As6Cl1.48O24.26Pb₁₀	V = 677.59 (3) Å³
M_r = 2962.16	Z = 1
Hexagonal, P6₃/m	Neutron radiation, λ = 1.8834 Å
a = 10.2415 (3) Å	T = 473 K
c = 7.4594 (2) Å	cylinder, ? × ? × ? mm

Data collection top

Local diffractometer	Data collection mode: reflection
Specimen mounting: vanadium can with He exchange gas	Scan method: Stationary detector

Refinement top

R_p = 0.049	χ² = 0.336
R_wp = 0.062	3001 data points
R_exp = 0.011	48 parameters
R_Bragg = 0.019	0 restraints

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

	x	y	z	B_iso*/B_eq	Occ. (<1)
Pb1	0.333333	0.666667	0.0046 (7)	2.3 (1)
Pb2	0.2506 (4)	0.0045 (5)	0.25	2.5 (1)
As1	0.4057 (4)	0.3807 (4)	0.25	0.9 (1)
O1	0.3280 (5)	0.4921 (6)	0.25	2.4 (1)
O2	0.5966 (6)	0.4826 (7)	0.2227 (15)	2.3 (2)	0.5
O3a	0.3317 (10)	0.2477 (10)	0.0903 (10)	1.9 (2)	0.5
O3b	0.3821 (9)	0.2895 (9)	0.0539 (9)	1.7 (2)	0.5
O4	0	0	0.25	2.5 (2)	0.13
Cl1	0	0	0	2.2 (1)	0.74

Experimental details

	(As6Cl2O18Pb10)	(As6Cl1.48O24.26Pb10_298K)	(As6Cl1.48O24.26Pb10_373K)	(As6Cl1.48O24.26Pb10_423K)
Crystal data
Chemical formula	As6Cl2O18Pb₁₀	As6Cl1.48O24.26Pb₁₀	As6Cl1.48O24.26Pb₁₀	As6Cl1.48O24.26Pb₁₀
M_r	2880.43	2962.16	2962.16	2962.16
Crystal system, space group	Hexagonal, P6₃/m	Hexagonal, P6₃/m	Hexagonal, P6₃/m	Hexagonal, P6₃/m
Temperature (K)	298	298	373	423
a, c (Å)	10.2972 (6), 7.0690 (6)	10.2055 (2), 7.4483 (2)	10.2224 (3), 7.4494 (2)	10.2323 (3), 7.4533 (2)
V (Å³)	649.12 (8)	671.83 (3)	674.15 (3)	675.82 (3)
Z	1	1	1	1
Radiation type	Neutron, λ = 1.8834 Å	Neutron, λ = 1.8834 Å	Neutron, λ = 1.8834 Å	Neutron, λ = 1.8834 Å
Specimen shape, size (mm)	Cylinder, ? × ? × ?	Cylinder, ? × ? × ?	Cylinder, ? × ? × ?	Cylinder, ? × ? × ?

Data collection
Diffractometer	Local diffractometer	Local diffractometer	Local diffractometer	Local diffractometer
Specimen mounting	Vanadium can with He exchange gas	Vanadium can with He exchange gas	Vanadium can with He exchange gas	Vanadium can with He exchange gas
Data collection mode	Reflection	Reflection	Reflection	Reflection
Scan method	Stationary detector	Stationary detector	Stationary detector	Stationary detector
2θ values (°)	2θ_fixed = ?	2θ_fixed = ?	2θ_fixed = ?	2θ_fixed = ?

Refinement
R factors and goodness of fit	R_p = 0.060, R_wp = 0.077, R_exp = 0.090, R_Bragg = 0.034, χ² = 0.740	R_p = 0.046, R_wp = 0.058, R_exp = 0.090, R_Bragg = 0.019, χ² = 0.423	R_p = 0.043, R_wp = 0.055, R_exp = 0.088, R_Bragg = 0.017, χ² = 0.397	R_p = 0.045, R_wp = 0.057, R_exp = 0.089, R_Bragg = 0.019, χ² = 0.423
No. of data points	3001	3001	3001	3001
No. of parameters	20	45	48	48

	(As6Cl1.48O24.26Pb10_473K)
Crystal data
Chemical formula	As6Cl1.48O24.26Pb₁₀
M_r	2962.16
Crystal system, space group	Hexagonal, P6₃/m
Temperature (K)	473
a, c (Å)	10.2415 (3), 7.4594 (2)
V (Å³)	677.59 (3)
Z	1
Radiation type	Neutron, λ = 1.8834 Å
Specimen shape, size (mm)	Cylinder, ? × ? × ?

Data collection
Diffractometer	Local diffractometer
Specimen mounting	Vanadium can with He exchange gas
Data collection mode	Reflection
Scan method	Stationary detector
2θ values (°)	2θ_fixed = ?

Refinement
R factors and goodness of fit	R_p = 0.049, R_wp = 0.062, R_exp = 0.011, R_Bragg = 0.019, χ² = 0.336
No. of data points	3001
No. of parameters	48

Computer programs: local, Shimadzu XRD 6000, TOPAS (Bruker, 2005), ATOMS (Shape, 2004), GFOURIER (Gonzales-Platas, J. & Rodriguez-Carvajal, J. (2006).

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