Exploring the Anomalous Phase Behavior of High-Pressure Ices in Diamond Confinement

A Goswami and JK Singh, JOURNAL OF PHYSICAL CHEMISTRY C, 124, 5460-5468 (2020).

DOI: 10.1021/acs.jpcc.9b11531

Inspired by the discovery of high-pressure ice inclusions in diamond, we investigate the rich structural diversity of high-pressure phases of quasi-two-dimensional water constrained by diamond matrices, using molecular dynamics simulations. Monolayer ices formed are structurally similar to monolayer ices constrained by graphene. We report new bilayer and trilayer ice phases, specifically, the AB II, ABC I, ABC II, and AAB/ABB ordered phases. The relative stability of the interlayer hydrogen bonds between adjacent layers reveals differences in structural properties. We observe grain-boundary migration between pockets of AAB and ABB ices, during the pressurization process. The compression-limit phase diagram in the slit width-lateral pressure plane has been constructed and analyzed. Our results indicate that the phase behavior of confined ice is qualitatively independent of the diamond-water force- field parameters and is significantly influenced by the lattice structure and confining surfaces.

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