Nastran, M., & Stöger, B. (2021). The order/disorder phase transition of hypophosphorous acid H₃PO₂. Zeitschrift Für Kristallographie - Crystalline Materials, 236(5–7), 163–172. https://doi.org/10.1515/zkri-2021-2014
Zeitschrift für Kristallographie - Crystalline Materials
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ISSN:
2194-4946
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Date (published):
24-Jun-2021
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Number of Pages:
10
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Publisher:
WALTER DE GRUYTER GMBH
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Peer reviewed:
Yes
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Keywords:
hydrogen bond; order/disorder phase transition; single crystal diffraction; topology
en
Abstract:
Hypophosphorous acid, H₃PO₂ is dimorphic with a phase transition in the 200-225 K range. The H₃PO₂ molecules are connected by hydrogen bonding to infinite chains extending in the [100] direction. In the high-temperature phase (P2₁2₁2, Z′=1/2), the hydrogen bonds are disordered about a two-fold rotation axis. On cooling below the phase transition temperature, the hydrogen bonds become ordered, resulting in a symmetry reduction of the klassengleiche type of index 2. In the low-temperature phase (P2₁2₁2₁, Z′=1), the c parameter is doubled with respect to the high-temperature phase. The hydrogen-bonding topology of the high- and low-temperature phases are double-infinite directed and undirected linear graphs, respectively.
