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The crystal chemistries of synthetic mimetite, Pb10(As5+O4)6(Cl2 - xOx/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.
Supporting information
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).
Crystal data top
As6Cl2O18Pb10 | F(000) = 288.5 |
Mr = 2880.43 | Dx = 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 |
Rp = 0.060 | Profile function: pseudo-Voigt |
Rwp = 0.077 | 20 parameters |
Rexp = 0.090 | 0 restraints |
RBragg = 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 |
Mr = 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
Rp = 0.060 | χ2 = 0.740 |
Rwp = 0.077 | 3001 data points |
Rexp = 0.090 | 20 parameters |
RBragg = 0.034 | 0 restraints |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | |
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 |
Mr = 2962.16 | Dx = 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 |
Rp = 0.046 | Profile function: pseudo-Voigt |
Rwp = 0.058 | 45 parameters |
Rexp = 0.090 | 0 restraints |
RBragg = 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 |
Mr = 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
Rp = 0.046 | χ2 = 0.423 |
Rwp = 0.058 | 3001 data points |
Rexp = 0.090 | 45 parameters |
RBragg = 0.019 | 0 restraints |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | 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 |
Mr = 2962.16 | Dx = 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 |
Rp = 0.043 | Profile function: pseudo-Voigt |
Rwp = 0.055 | 48 parameters |
Rexp = 0.088 | 0 restraints |
RBragg = 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 |
Mr = 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
Rp = 0.043 | χ2 = 0.397 |
Rwp = 0.055 | 3001 data points |
Rexp = 0.088 | 48 parameters |
RBragg = 0.017 | 0 restraints |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | 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 |
Mr = 2962.16 | Dx = 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 |
Rp = 0.045 | Profile function: pseudo-Voigt |
Rwp = 0.057 | 48 parameters |
Rexp = 0.089 | 0 restraints |
RBragg = 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 |
Mr = 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
Rp = 0.045 | χ2 = 0.423 |
Rwp = 0.057 | 3001 data points |
Rexp = 0.089 | 48 parameters |
RBragg = 0.019 | 0 restraints |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | 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 |
Mr = 2962.16 | Dx = 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 |
Rp = 0.049 | Profile function: pseudo-Voigt |
Rwp = 0.062 | 48 parameters |
Rexp = 0.011 | 0 restraints |
RBragg = 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 |
Mr = 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
Rp = 0.049 | χ2 = 0.336 |
Rwp = 0.062 | 3001 data points |
Rexp = 0.011 | 48 parameters |
RBragg = 0.019 | 0 restraints |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | 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 |
Mr | 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 (°) | 2θfixed = ? | 2θfixed = ? | 2θfixed = ? | 2θfixed = ? |
|
Refinement |
R factors and goodness of fit | Rp = 0.060, Rwp = 0.077, Rexp = 0.090, RBragg = 0.034, χ2 = 0.740 | Rp = 0.046, Rwp = 0.058, Rexp = 0.090, RBragg = 0.019, χ2 = 0.423 | Rp = 0.043, Rwp = 0.055, Rexp = 0.088, RBragg = 0.017, χ2 = 0.397 | Rp = 0.045, Rwp = 0.057, Rexp = 0.089, RBragg = 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 |
Mr | 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 (°) | 2θfixed = ? |
|
Refinement |
R factors and goodness of fit | Rp = 0.049, Rwp = 0.062, Rexp = 0.011, RBragg = 0.019, χ2 = 0.336 |
No. of data points | 3001 |
No. of parameters | 48 |
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