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Six-fold-coordinated phosphorus by oxygen in AlPO4 quartz homeotype under high pressure


AlPO4 belongs to the berlinite quartz homeotype family, which has been the subject of intense high-pressure research triggered by the supposed existence of reversible pressure-induced amorphization. X-ray diffraction experiments, complemented with ab initio calculations, demonstrate the existence of two high-pressure crystalline polymorphs and show that AlPO4 shares the same two-stage densification mechanism as silica. In the first step, a compact hexagonal sublattice of oxygen atoms is formed. In the second step, the cations redistribute in the interstices giving rise to a monoclinic distorted CaCl2 phase. The most outstanding feature of the phase is that phosphorous becomes six-fold coordinated by oxygen, adopting a configuration unknown so far in solid-state science. This finding opens possibilities in the high-pressure chemistry of phosphorus. The close relationship of AlPO4 with silica suggests the existence of completely unexplored families of compounds analogous to those of six-fold-coordinated silicates but based on PO6.

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Figure 1: ADXRD diffraction spectra under high pressure.
Figure 2: Rietveld refinements.
Figure 3: AlPO4 high-pressure polymorphs.
Figure 4: AlPO4 lattice parameters.
Figure 5: AlPO4 equation of state.
Figure 6: Relative enthalpy of several AlPO4 polymorphs.


  1. Haines, J. & Cambon, O. The effects of pressure, temperature and composition on the crystal structures of α-quartz homeotypes. Z. Krystallogr. 219, 314–323 (2004).

    CAS  Google Scholar 

  2. Kruger, M. B. & Jeanloz, R. Memory glass: An amorphous material formed from AlPO4 . Science 249, 647–649 (1990).

    Article  CAS  Google Scholar 

  3. Polian, A., Grimsditch, M. & Philippot, E. Memory effects in pressure induced amorphous AlPO4 . Phys. Rev. Lett. 71, 3143–3145 (1993).

    Article  CAS  Google Scholar 

  4. Tse, J. S. & Klug, D. D. Structural memory in pressure-amorphized AlPO4 . Science 255, 1559–1561 (1992).

    Article  CAS  Google Scholar 

  5. Chaplot, S. L. & Sikka, S. K. Molecular-dynamics simulation of pressure-induced crystalline-to-amorphous transition in some corner-linked polyhedral compounds. Phys. Rev. B 47, 5710–5714 (1993).

    Article  CAS  Google Scholar 

  6. Garg, N. & Sharma, S. M. A molecular dynamical investigation of high pressure phase transformations in berlinite (α-AlPO4). J. Phys. Condens. Matter 12, 375–397 (2000).

    Article  CAS  Google Scholar 

  7. Gillet, P., Badro, J., Varrel, B. & McMillan, P. F. High-pressure behaviour in α-AlPO4: Amorphization and the memory-glass effect. Phys. Rev. B 51, 11262–11269 (1995).

    Article  CAS  Google Scholar 

  8. Sharma, S. M., Garg, N. & Sikka, S. K. High-pressure X-ray-diffraction study of α-AlPO4 . Phys. Rev. B 62, 8824–8827 (2000).

    Article  CAS  Google Scholar 

  9. Sharma, S. M., Garg, N. & Sikka, S. K. High-pressure phase transformations in α-AlPO4: an X-ray diffraction investigation. J. Phys. Condens. Matter 12, 6683–6692 (2000).

    Article  CAS  Google Scholar 

  10. Ramaniah, L. M., Sharma, S. M., Kunc, K., Garg, N. & Laghate, M. First-principles determination of the relative stability of the α and Cmcm structures of AlPO4 . Phys. Rev. B 68, 014119 (2003).

    Article  Google Scholar 

  11. Badro, J., Gillet, Ph., McMillan, P. F., Polian, A. & Itié, J. P. A combined XAS and XRD study of the high-pressure behaviour of GaAsO4 berlinite. Europhys. Lett. 40, 533–538 (1997).

    Article  CAS  Google Scholar 

  12. Polian, A., Itié, J. P., Grimsditch, M., Badro, J. & Philippot, E. Berlinites under pressure. Eur. J. Solid State Inorg. Chem. 34, 669–678 (1997).

    CAS  Google Scholar 

  13. Santamaría-Pérez, D., Haines, J., Amador, U., Morán, E. & Vegas, A. Structural characterization of a new high-pressure phase of GaAsO4 . Acta Cryst. B 62, 1019–1024 (2006).

    Article  Google Scholar 

  14. Matar, S., Lelogeais, M., Michau, D. & Demazeau, G. Investigations of the high pressure varieties of GaAsO4 . Mater. Lett. 10, 45–48 (1990).

    Article  CAS  Google Scholar 

  15. Badro, J., Itié, J. P. & Polian, A. On the high-pressure phase transition in GaPO4 . Eur. Phys. J. B 1, 265–268 (1998).

    Article  CAS  Google Scholar 

  16. Mooney, R. C. L. Crystal structure of anhydrous indium phosphate and thallic phosphate by X-ray diffraction. Acta Cryst. 9, 113–117 (1956).

    Article  CAS  Google Scholar 

  17. Marton^ák, R., Donadio, D., Oganov, A. R. & Parrinello, M. Crystal structure transformations in SiO2 from classical and ab initio metadynamics. Nature Mater. 5, 623–626 (2006).

    Article  Google Scholar 

  18. Tsuneyuki, S., Matsui, Y., Aoki, H. & Tsukada, M. New pressure-induced structural transformations in silica obtained by computer simulation. Nature 339, 209–211 (1989).

    Article  CAS  Google Scholar 

  19. Birch, F. Finite strain isotherm and velocities for single-crystal and polycrystalline NaCl at high-pressures and 300-degree-K. J. Geophys. Res. 83, 1257–1268 (1978).

    Article  CAS  Google Scholar 

  20. Tsuchida, Y. & Yagi, T. A new, post-stishovite high pressure polymorph of silica. Nature 340, 217–220 (1989).

    Article  CAS  Google Scholar 

  21. Andrault, D., Angel, R. J., Mosenfelder, J. L. & Le Bihan, T. Equation of state of stishovite to lower mantle pressures. Am. Mineral. 88, 301–307 (2003).

    Article  CAS  Google Scholar 

  22. Teter, D. M., Hemley, R. J., Kresse, G. & Hafner, J. High pressure polymorphism in silica. Phys. Rev. Lett. 80, 2145–2148 (1998).

    Article  CAS  Google Scholar 

  23. Kingma, K. J., Cohen, R. E., Hemley, R. J. & Mao, H. K. Transformation of stishovite to a denser phase at lower-mantle pressures. Nature 374, 243–245 (1995).

    Article  CAS  Google Scholar 

  24. Huang, L., Durandurdu, M. & Kieffer, J. Transformations pathways of silica under high pressure. Nature Mater. 5, 977–981 (2006).

    Article  CAS  Google Scholar 

  25. Finger, L. W. & Hazen, R. M. Crystal chemistry of six-coordinated silicon: A key to understanding the earth’s deep interior. Acta Cryst. B 47, 561–580 (1991).

    Article  Google Scholar 

  26. Galy, J. & Miehe, G. Ab initio structures of (M2) and (M3) VO2 high pressure phases. Solid State Sci. 1, 443–448 (1999).

    Article  Google Scholar 

  27. Mao, H., Xu, J. & Bell, P. Calibration of the ruby pressure gauge to 800-kbar under quasi-hydrostatic conditions. J. Geophys. Res. 91, 4673–4676 (1986).

    Article  CAS  Google Scholar 

  28. Chervin, J. C., Canny, B. & Mancinelli, M. Ruby-spheres as pressure gauge for optically transparent high pressure cells. High Press. Res. 21, 305–314 (2002).

    Article  Google Scholar 

  29. Couzinet, B., Dahan, N., Hamel, G. & Chervin, J. C. Optically monitored high-pressure gas loading apparatus for diamond anvil cells. High Press. Res. 23, 409–415 (2003).

    Article  Google Scholar 

  30. Hammersley, A. P. ESRF Internal Report, ESRF97HA02T, “FIT2D: An introduction and Overview” (ESRF, 1995).

  31. Hammersley, A. P., Svensson, S. O., Hanfland, M., Fitch, A. N. & Häusermann, D. Two-dimensional detector software: From real detector to idealised image or two-theta scan. High Press. Res. 14, 235–248 (1996).

    Article  Google Scholar 

  32. Boultif, A. & Louer, D. Powder pattern indexing with the dichotomy method. J. Appl. Cryst. 37, 724–731 (2004).

    Article  CAS  Google Scholar 

  33. Larson, A. C. & Von Dreele, R. B. General Structure Analysis System (GSAS). Los Alamos National Laboratory Report LAUR 86-748 (2004).

  34. Burke, K., Perdew, J. P. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865 (1996).

    Article  Google Scholar 

  35. Baroni, S., de Gironcoli, S., Corso, A. D. & Giannozzi, P. Phonons and related crystal properties from density-functional perturbation theory. Rev. Mod. Phys. 73, 515–562 (2001).

    Article  CAS  Google Scholar 

  36. Vanderbilt, D. Soft self-consistent pseudopotentials in a generalized eigenvalue formalism. Phys. Rev. B 41, 7892 (1990).

    Article  CAS  Google Scholar 

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We thank M. A. Alario for a critical reading of the manuscript. We acknowledge the Ministerio de Educación y Ciencia of Spain (project BFM2001-3309-C02-01/02). A.M.S. acknowledges the French National Supercomputing Facility IDRIS, where the calculations have been carried out under the projects CP9-61387 and CP9-71387.

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Correspondence to Julio Pellicer-Porres.

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Pellicer-Porres, J., Saitta, A., Polian, A. et al. Six-fold-coordinated phosphorus by oxygen in AlPO4 quartz homeotype under high pressure. Nature Mater 6, 698–702 (2007).

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