Solid hydrogen, density

The results in Table V illustrate that MD studies, compared to the MC results in Table IV, facilitate the investigation of transport and time-dependent properties. Also, they show that use of the MCY potential leads to very large density oscillations and increasing water density near the surfaces. This appears to be a serious drawback to the use of the MCY potential in simulations of interfacial water. Results from the investigations using the ST2 potential show that interfacial water density is approximately 1.0 g/cc, with a tendency for decreased density and hydrogen bonding near the surfaces. As in the MC simulations, orientations of the water dipole moment are affected by the presence of a solid/liquid interface, and an... 

Figure 5.11 Hydrogen density for compressed hydrogen, liquid and solid hydrogen.

The dielectric constant values in Table 2.8 also suggest that, while hydrate water molecules reorient rapidly compared to molecules in other solids, reorientation rates are only one-half those in ice. The hydrate value is lower than that of ice due to the lower density of hydrogen-bonded water molecules. 

D. Colognesi, C. Andreani E. Degiorgi (2003). J. Neutron Res., 11,123-143. Phonon density of states from a crystal analyzer inverse-geometry spectrometer a study on ordered solid hydrogen sulfide and hydrogen chloride. 

Although these simplified models of hydrogen-bonded systems give a far from complete picture of the solid-fluid phase behavior of water, this kind of approach to identifying the key features required in the molecular model is an instructive one. Indeed, the inability of the PMW to generate reentrant melting of the low-density solid at thermodynamically stable states is an important result. It shows us that more than just short-range directional forces are required for this to occur. 

At very high pressures (>2 x 10 Pa), solid hydrogen is expected [15] to transform from a diatomic molecular phase to a monatomic metallic phase with a density >1000 kgm. This phase may become a high-temperature superconductor [16] (Tables 4.4 and 4.5). 

Solid hydrogen has an even higher density than liquid hydrogen. For some applications (space) slush is sometimes used, a mixture of liquid with solid hydrogen. This mixture exists only at or near the Triple point of hydrogen (13.8 K, 7040 Pa). Production and handling of slush are associated with a number... 

---