Abstract
The solid-state chemistry of superficially mundane A2BX4 compounds with β-K2SO4-related structures is ‘a can of worms’, characterized by prolific polymorphism and, despite careful single-crystal X-ray diffraction studies, persistent uncertainty about exact space groups and atom positions. This is true of Ca2SiO41–7, a major constituent of cement, and Sr2SiO48–10 despite 50 years of (confusing) literature. On the other hand, the solid-state physics of some other A2BX4 compounds (for example, K2SeO4), as well as more exotic charge-density-wave types, involves modulated structures. Similar behaviour could conceivably resolve the structural confusion cited above (wrong structural models may have been refined); to investigate this possibility11 we have studied the transition β- → α′-Sr2SiO4 by beam-heating the β-polymorph in an electron microscope. Electron diffraction patterns reveal two sets of incommensurate satellite reflections, indicating distinct modulated structures. Their origin is an asymmetric —Sr—O—Sr—O— chain (common to β and α′), with alternating bond lengths which tend to equality as T increases, but at a cost of reduced total bond strength and energy.
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Smith, D. K., Majumdar, A. & Ordway, F. Acta crystallogr. 18, 787–795 (1965).
Eysel, W. & Hahn, T. Z. Kristallogr. 131, 322–341 (1970).
Saalfeld, H. Am. Miner. 60, 824–827 (1975).
Moore, P. B. & Araki, T. Am. Miner. 61, 74–87 (1976).
Barnes, P., Fentiman, C. H. & Jeffrey, J. W. Acta crystallogr. A36, 353–356 (1980).
Sarkar, S. L. J. Mater. Sci. 15, 1324–1325 (1980).
Eysel, W., Höfer, H. H., Keester, K. L. & Hahn, T. Acta crystallogr. B41, 5–11 (1985).
Catti, M., Gazzoni, G. & Ivaldi, G. Acta crystallogr. C39, 29–34, (1983).
Catti, M., Gazzoni, G., Ivaldi, G. & Zanini, G. Acta crystallogr. B39, 674–679 (1983).
Catti, M. & Ivaldi, G. Acta crystallogr. B40, 537–544 (1984).
Barbier, J. & Hyde, B. G. Acta crystallogr. B41, 383–390 (1985).
Regourd, M., Bigare, M., Forest, J. & Guinier, A. 5th int. Symp. Chemistry of Cement, Tokyo, Vol. 1, 44–48 (The Cement Association of Japan, 1968).
Catti, M. & Gazzoni, G. Acta crystallogr. B39, 679–684 (1983).
Groves, G. W. J. Mater. Sci. 18, 1615–1624 (1983).
Iizumi, M., Axe, J. D., Shirane, G. & Shimaoka, K. Phys. Rev. B15, 4392–4411 (1977).
Altermatt, D., Arend, H., Gramlich, V., Niggli, A. & Petter, W. Acta crystallogr. B40, 347–350 (1984).
Brown, I.D. in Structure and Bonding in Crystals Vol. 2 (eds O'Keeffe, M. & Navrotsky, A.) (Academic, New York, 1981).
Pynn, R. Nature 281, 433–437 (1979).
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Stenberg, L., Sellar, J. & Hyde, B. Incommensurately modulated α′-Sr2SiO4. Nature 320, 428–429 (1986). https://doi.org/10.1038/320428a0
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DOI: https://doi.org/10.1038/320428a0
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