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A new high‐pressure polymorph of phosphoric acid
Author(s) -
Bull Craig L.,
Funnell Nicholas P.,
Pulham Colin R.,
Marshall William G.,
Allan David R.
Publication year - 2017
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s205252061701441x
Subject(s) - orthorhombic crystal system , monoclinic crystal system , crystallography , materials science , phase (matter) , bulk modulus , molecule , neutron diffraction , diffraction , phosphoric acid , crystal structure prediction , crystal structure , thermodynamics , chemistry , organic chemistry , composite material , physics , optics , metallurgy
The high‐pressure structural behaviour of phosphoric acid is described. A compression study of the monoclinic phase, using neutron powder diffraction and X‐ray single‐crystal diffraction, shows that it converts to a previously unobserved orthorhombic phase on decompression. Compression of this new phase is reported up to 6.3 GPa. The orthorhombic phase is found to be more efficiently packed, with reduced void space, resulting in a larger bulk modulus. Molecule–molecule interaction energies reveal a more extensive network of increased attractive forces in the orthorhombic form relative to the monoclinic form, suggesting greater thermodynamic stability.