research papers
Calcium aluminate decahydrate is hexagonal with the space group P63/m and Z = 6. The compound has been named CaAl2O4·10H2O (CAH10) for decades and is known as the product obtained by hydration of CaAl2O4 (CA) in the temperature region 273–288 K – one of the main components in high-alumina cements. The lattice constants depend on the water content. Several sample preparations were used in this investigation: one CAH10, three CAD10 and one CA(D/H)10, where the latter is a zero-matrix sample showing no coherent scattering contribution from the D/H atoms in a neutron diffraction powder pattern. The crystal structure including the positions of the H/D atoms was determined from analyses of four neutron diffraction powder patterns by means of the ab initio crystal structure determination program FOX and the FULLPROF crystal structure refinement program. Additionally, eight X-ray powder diffraction patterns (Cu Kα1 and synchrotron X-rays) were used to establish phase purity. The analyses of these combined neutron and X-ray diffraction data clearly show that the previously published positions of the O atoms in the water molecules are in error. Thermogravimetric analysis of the CAD10 sample preparation used for the neutron diffraction studies gave the composition CaAl2(OD)8(D2O)2·2.42D2O. Neutron and X-ray powder diffraction data gave the structural formula CaAl2(OX)8(X2O)2·γX2O (X = D, H and D/H), where the γ values are sample dependent and lie between 2.3 and 3.3.
Keywords: high-alumina cements; neutron and X-ray powder diffraction; calcium aluminate decahydrate; thermogravimetric analysis.
Supporting information
(C3-2K) top
Crystal data top
CaAl2O48.42D2O | V = 1905.11 Å3 |
Mr = 326.67 | Z = 6 |
Hexagonal, P63/M | Neutron radiation, λ = 1.885400 Å |
Hall symbol: -P 6c | T = 2 K |
a = 16.30365 Å | white |
c = 8.27597 Å | ?, ? × ? × ? mm |
Data collection top
HRPT at SINQ diffractometer | Scan method: step |
Radiation source: neutron spallation source, HRPT at SINQ, CH-5232 Villigen PSI, Switzerland | 2θmin = 4.057°, 2θmax = 164.857°, 2θstep = 0.100° |
Ge hkk monochromator |
Refinement top
Rp = 2.264 | 1609 data points |
Rwp = 2.985 | 68 parameters |
Rexp = 0.641 | 30 restraints |
RBragg = 8.392 | (Δ/σ)max = 0.05 |
χ2 = 18.900 |
Crystal data top
CaAl2O48.42D2O | V = 1905.11 Å3 |
Mr = 326.67 | Z = 6 |
Hexagonal, P63/M | Neutron radiation, λ = 1.885400 Å |
a = 16.30365 Å | T = 2 K |
c = 8.27597 Å | ?, ? × ? × ? mm |
Data collection top
HRPT at SINQ diffractometer | 2θmin = 4.057°, 2θmax = 164.857°, 2θstep = 0.100° |
Scan method: step |
Refinement top
Rp = 2.264 | χ2 = 18.900 |
Rwp = 2.985 | 1609 data points |
Rexp = 0.641 | 68 parameters |
RBragg = 8.392 | 30 restraints |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Al | 0.5877 (8) | 0.5038 (11) | 0.0712 (13) | 0.01267* | |
Ca | 0.5154 (13) | 0.2625 (17) | 0.2500 | 0.01267* | |
O1 | 0.6674 (14) | 0.564 (2) | 0.2500 | 0.01267* | |
D1 | 0.6990 (12) | 0.6373 (18) | 0.2500 | 0.02533* | |
O2 | 0.5203 (10) | 0.5728 (13) | 0.0833 (18) | 0.01267* | |
D2 | 0.5736 (9) | 0.6462 (12) | 0.0917 (19) | 0.02533* | |
O3 | 0.5179 (11) | 0.4217 (15) | 0.2500 | 0.01267* | |
D3 | 0.4560 (11) | 0.4293 (16) | 0.2500 | 0.02533* | |
O4 | 0.6858 (9) | 0.5773 (14) | −0.0698 (14) | 0.01267* | |
D4 | 0.6623 (10) | 0.5853 (15) | −0.1869 (13) | 0.02533* | |
O5 | 0.6184 (10) | 0.4086 (13) | 0.0616 (15) | 0.01267* | |
D5 | 0.6442 (12) | 0.3979 (14) | −0.0378 (15) | 0.02533* | |
O9 | 0.3948 (8) | 0.2490 (11) | 0.0396 (16) | 0.01267* | |
D91 | 0.3160 (8) | 0.2121 (13) | 0.0783 (19) | 0.02533* | |
D92 | 0.4152 (10) | 0.2012 (13) | 0.005 (2) | 0.02533* | |
O6 | 0.1890 (13) | 0.3445 (13) | 0.2500 | 0.01267* | 0.422 (14) |
D61 | 0.1106 (12) | 0.3064 (18) | 0.2500 | 0.02533* | 0.422 (14) |
D62 | 0.215 (2) | 0.4226 (10) | 0.2500 | 0.02533* | 0.422 (14) |
O7 | −0.004 (2) | 0.8967 (19) | 0.091 (3) | 0.01267* | 0.461 (5) |
D71 | 0.002 (2) | 0.9279 (18) | 0.213 (2) | 0.02533* | 0.461 (5) |
D72 | 0.023 (2) | 0.8483 (18) | 0.086 (3) | 0.02533* | 0.461 (5) |
O8 | 0.2310 (12) | 0.2308 (16) | −0.040 (2) | 0.01267* | 0.539 (5) |
D81 | 0.2499 (16) | 0.215 (2) | 0.071 (3) | 0.02533* | 0.539 (5) |
D82 | 0.1551 (12) | 0.1899 (18) | −0.068 (3) | 0.02533* | 0.539 (5) |
Experimental details
Crystal data | |
Chemical formula | CaAl2O48.42D2O |
Mr | 326.67 |
Crystal system, space group | Hexagonal, P63/M |
Temperature (K) | 2 |
a, c (Å) | 16.30365, 8.27597 |
V (Å3) | 1905.11 |
Z | 6 |
Radiation type | Neutron, λ = 1.885400 Å |
Specimen shape, size (mm) | ?, ? × ? × ? |
Data collection | |
Diffractometer | HRPT at SINQ diffractometer |
Specimen mounting | ? |
Data collection mode | ? |
Scan method | Step |
2θ values (°) | 2θmin = 4.057 2θmax = 164.857 2θstep = 0.100 |
Refinement | |
R factors and goodness of fit | Rp = 2.264, Rwp = 2.985, Rexp = 0.641, RBragg = 8.392, χ2 = 18.900 |
No. of data points | 1609 |
No. of parameters | 68 |
No. of restraints | 30 |
Computer programs: FULLPROF.