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A new high-pressure polymorph of phosphoric acid

DOI: 10.1107/S205252061701441X DOI Help

Authors: Craig L. Bull (ISIS Facility) , Nicholas P. Funnell (ISIS Facility) , Colin R. Pulham (EaStCHEM School of Chemistry) , William G. Marshall (ISIS Facility) , David R. Allan (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acta Crystallographica Section B Structural Science, Crystal Engineering And Materials , VOL 73 , PAGES 1068 - 1074

State: Published (Approved)
Published: December 2017

Abstract: 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.

Journal Keywords: high pressure; neutron powder diffraction; X-ray single-crystal diffraction; phosphoric acid; polymorph

Subject Areas: Physics

Facility: ISIS