Stability of hydrogen-filled hexagonal ice under high pressure
1Department of Chemistry, Zhejiang University, Hangzhou 310028, People's Republic of China.
Abstract:
Hydrogen hydrates, composed of a water (H2O) host framework enclosing hydrogen (H2) molecules, exhibit diverse crystal structures. The stability of their high-pressure phases provides fundamental insight into the constituents of giant planets-rich in both H2O and H2-as well as their potential for energy storage on Earth. While H2-filled ice Ic (C2 hydrate) is known to be stable above 2 GPa, the possible existence of H2-filled ice Ih (named CIh hydrate) has remained largely unexplored. Here, we employ hybrid grand-canonical Monte Carlo and isothermal-isobaric molecular dynamics simulations to demonstrate that ice Ih can absorb H2 up to an H2-to-H2O ratio of 0.5 upon compression. Moreover, free energy calculations reveal that CIh hydrate becomes thermodynamically stable under a few gigapascals, thereby occupying the stability conditions previously attributed to C1 hydrate.
Related Concept Videos
02:34Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility
Temporary attractive forces like dispersion are present in all molecules, whether they are polar or nonpolar. They...
02:11Conformations of Cyclohexane
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal...
01:04Hydrogen Bonds
00:26Hydrogen Bonds
Hydrogen Bonds Control the World!
Because hydrogen has very weak electronegativity when it binds with a strongly electronegative atom, such as oxygen or nitrogen, electrons in the bond are unequally shared....
02:39Phase Transitions: Melting and Freezing
02:30Stability of Substituted Cyclohexanes
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...