What question did this study set out to answer?

Determine the crystallographic structure, framework coordination, and proton ordering behavior of ice V under high-pressure conditions.

Structure of ice. V

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Crystallographic analysis reveals a distorted monoclinic tetrahedral framework in ice V, indicating persistent proton disorder at low temperatures.

Determine the crystallographic structure, framework coordination, and proton ordering behavior of ice V under high-pressure conditions.
Analyzed the monoclinic crystal structure of ice V quenched to 120 K, representative of the 3 to 6 kbar stability regime.
Evaluated oxygen framework coordination, bond distances, bond angles, and space group constraints using X-ray structural evidence.
Ice V crystallizes in monoclinic space group A2/a (a = 9.22 Å, b = 7.54 Å, c = 10.35 Å, β = 109.2°) with 28 molecules per unit cell and a density of 1.23 g·cm⁻³.
The structure forms a single tetrahedral framework where oxygen atoms link to 4 neighbors at distances of 2.76–2.87 Å (mean 2.80 Å) with bond angles spanning 84° to 128° (root-mean-square deviation 18° from ideal tetrahedral coordination).
Proton ordering is incompatible with space group A2/a, establishing that ordering energy must remain below 0.14 kcal·mol⁻¹ to retain disorder upon quenching to 120 K.

Kamb et al. (1967) studied this question.

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Crystallographic analysis reveals a distorted monoclinic tetrahedral framework in ice V, indicating persistent proton disorder at low temperatures.