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The crystal structures of two new high-pressure AlPO
4 phases are reported. One phase synthesized at 6 GPa and 1523 K is triclinic (
) whilst the other phase synthesized at 7 GPa and 1773 K is monoclinic (
).
31P MAS (magic-angle spinning) NMR suggests three tetrahedral P sites with equal abundance in both phases.
27Al 3Q MAS NMR spectra provided evidence for two octahedral sites and one five-coordinated Al site in each phase. The crystal structures were solved using an
ab initio structure determination technique from synchrotron powder X-ray diffraction data utilizing the local structural information from NMR, and were further refined by the Rietveld method. Both phases contain doubly bent chains made of six edge-shared Al polyhedra (including five-coordinated Al), which are joined by PO
4 tetrahedra. The
phase is isostructural with FeVO
4 and AlVO
4. The two phases differ in the packing manner of the chains. This study has demonstrated that the combined application of
ab initio structure determination
via X-ray powder diffraction and solid-state NMR spectroscopy is a powerful approach to the rapid solution of complex inorganic crystal structures.
Supporting information
For both structures, program(s) used to solve structure: FOX; program(s) used to refine structure: RIETAN-FP; molecular graphics: VESTA.
Crystal data top
AlO4P | V = 365.9 (1) Å3 |
Mr = 121.95 | Z = 6 |
Triclinic, P1 | Synchrotron radiation, λ = 1.00036 Å |
a = 6.1328 (1) Å | µ = 3.24 mm−1 |
b = 7.5151 (1) Å | T = 300 K |
c = 8.5801 (1) Å | Particle morphology: powder |
α = 98.2630 (7)° | white |
β = 104.6220 (8)° | cylinder, 3.0 × 0.3 mm |
γ = 102.1398 (8)° | Specimen preparation: Prepared at 1523 K and 6000000 kPa, cooled at 30000 K min−1 |
Data collection top
Debye-Scherrer diffractometer | Data collection mode: transmission |
Radiation source: synchrotron, SR | Scan method: step |
Specimen mounting: capillary | 2θmin = 5.910°, 2θmax = 76.990°, 2θstep = 0.010° |
Refinement top
Rp = 0.033 | Profile function: Splitted Pseudo-Voigt |
Rwp = 0.045 | 130 parameters |
Rexp = 0.031 | 0 restraints |
RBragg = 0.017 | 39 constraints |
6886 data points | Background function: Legendre polynomial x background data |
Excluded region(s): 0-5.9, 8.7-9.3, 12.8-13.7, 15.0-15.7, 77.0-80 | Preferred orientation correction: March-Dollase function |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | |
Al1 | 0.7618 (4) | 0.6879 (4) | 0.4185 (3) | 0.89 (6)* | |
Al2 | 0.4695 (4) | 0.8960 (4) | 0.2105 (3) | 0.93 (6)* | |
Al3 | 0.9820 (5) | 0.3015 (4) | 0.0226 (3) | 0.76 (5)* | |
P1 | 0.0083 (4) | 0.0074 (3) | 0.2594 (2) | 0.97 (5)* | |
P2 | 0.1993 (3) | 0.5970 (3) | 0.3444 (3) | 1.07 (5)* | |
P3 | 0.5223 (4) | 0.3020 (3) | 0.1316 (3) | 1.00 (5)* | |
O11 | 0.9463 (7) | 0.1423 (6) | 0.1537 (5) | 0.89 (6)* | |
O12 | 0.7696 (8) | 0.8770 (6) | 0.2642 (3) | 0.89 (6)* | |
O13 | 0.1342 (7) | 0.8740 (6) | 0.1690 (5) | 0.89 (6)* | |
O14 | 0.1768 (7) | 0.0967 (6) | 0.4309 (5) | 0.89 (6)* | |
O21 | 0.0558 (7) | 0.5307 (6) | 0.1543 (4) | 0.71 (5)* | |
O22 | 0.2652 (7) | 0.4339 (6) | 0.4180 (5) | 0.71 (5)* | |
O23 | 0.0650 (7) | 0.7026 (6) | 0.4317 (5) | 0.71 (5)* | |
O24 | 0.4380 (8) | 0.7370 (5) | 0.3525 (5) | 0.71 (5)* | |
O31 | 0.3516 (7) | 0.7298 (5) | 0.0127 (5) | 0.96 (6)* | |
O32 | 0.5181 (7) | 0.1299 (5) | 0.2119 (5) | 0.96 (6)* | |
O33 | 0.2772 (7) | 0.3054 (6) | 0.0374 (5) | 0.96 (6)* | |
O34 | 0.6533 (6) | 0.4772 (6) | 0.2497 (5) | 0.96 (6)* | |
Crystal data top
AlO4P | Z = 12 |
Mr = 121.95 | Synchrotron radiation, λ = 1.00036 Å |
Monoclinic, P21/c | µ = 3.25 mm−1 |
a = 6.13219 (6) Å | T = 300 K |
b = 14.3465 (1) Å | Particle morphology: powder |
c = 8.57620 (9) Å | white |
β = 104.7426 (5)° | cylinder, 3.0 × 0.3 mm |
V = 729.7 (1) Å3 | Specimen preparation: Prepared at 1773 K and 7000000 kPa, cooled at 30000 K min−1 |
Data collection top
Debye-Scherrer diffractometer | Data collection mode: transmission |
Radiation source: synchrotron, SR | Scan method: step |
Specimen mounting: capillary | 2θmin = 7.010°, 2θmax = 77.490°, 2θstep = 0.010° |
Refinement top
Rp = 0.036 | Profile function: Pseudo-Voigt |
Rwp = 0.049 | 145 parameters |
Rexp = 0.031 | 0 restraints |
RBragg = 0.021 | 0 constraints |
7049 data points | Weighting scheme based on measured s.u.'s |
Excluded region(s): 0-7, 77.5-80 | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | |
Al1 | 0.7963 (3) | 0.5921 (1) | 0.6194 (2) | 0.79 (4)* | |
Al2 | 0.1559 (4) | 0.6988 (1) | 0.8504 (2) | 0.85 (4)* | |
Al3 | 0.4535 (3) | 0.1023 (1) | 0.4374 (2) | 0.81 (4)* | |
P1 | 0.3214 (3) | 0.2484 (1) | 0.1412 (2) | 0.96 (3)* | |
P2 | 0.6681 (3) | 0.0474 (1) | 0.8262 (2) | 1.07 (4)* | |
P3 | 0.9140 (3) | 0.1027 (1) | 0.3284 (2) | 0.98 (3)* | |
O11 | 0.4271 (6) | 0.1809 (2) | 0.2734 (4) | 0.89 (8)* | |
O12 | 0.1566 (6) | 0.3211 (2) | 0.1907 (5) | 0.86 (8)* | |
O13 | 0.5212 (6) | 0.3057 (3) | 0.0988 (5) | 1.02 (9)* | |
O14 | 0.1792 (6) | 0.2042 (2) | 0.9896 (4) | 0.51 (8)* | |
O21 | 0.5466 (6) | 0.0144 (2) | 0.6494 (4) | 0.83 (9)* | |
O22 | 0.7705 (6) | 0.9662 (2) | 0.9264 (5) | 0.67 (8)* | |
O23 | 0.5052 (6) | 0.1054 (3) | 0.8955 (4) | 0.99 (8)* | |
O24 | 0.8652 (6) | 0.1143 (3) | 0.8068 (4) | 0.77 (8)* | |
O31 | 0.7815 (5) | 0.1243 (2) | 0.4700 (4) | 0.69 (9)* | |
O32 | 0.8616 (6) | 0.1881 (2) | 0.2109 (4) | 1.13 (9)* | |
O33 | 0.1633 (6) | 0.0946 (3) | 0.4195 (4) | 0.94 (8)* | |
O34 | 0.8310 (6) | 0.0121 (2) | 0.2476 (4) | 0.77 (8)* | |
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