HELIUM, SOLID 3 Helium, the Quantum Solid The basic character of solid helium is revealed in the specific heat, Cp v, arising from vibration of the atoms about their lattice points, the phonons (p). At low temperature (T), Cp v is well described in all phases by the traditional Debye expression Cp v = 3R µ 4π4 5 ¶µ T θD ¶3. (1)

At higher temperatures, helium will solidify with sufficient pressure. At room temperature, this requires about 114,000 atm. [111] Helium-4 and helium-3 both form several crystalline solid phases, all requiring at least 25 bar.

Helium can be made solid at room temperature if the pressure rises to about 114 thousand atmospheres: that is a pressure of 1.67 million psi, or 834 tons per square inch. This is over 100 times greater than the pressure at the oceans’ deepest point, the Challenger Deep, which is almost seven miles deep (10 916 meters).

Helium is the only substance that remains liquid at absolute zero of temperature, 0 K (zero Kelvin), or -273.15 Celsius. All other substances solidify at temperatures higher than 10 K, see a typical phase diagram .

1988年7月20日 · Helium solidifies at 300 K and 11.5 GPa [35], which is sufficiently far from the HP-I to HP-II transition that any influence can be disregarded, and solid helium remains extremely soft in ...

Molecule phase diagram showing the transition phases between solid, liquid and gas as a function of temperature and pressure

Shown to the right is the phase diagram for helium (He). A.What is the maximum temperature for which “superfluid” helium-II exists? B.What is the minimum pressure at which solid helium can exist? C.What is the normal boiling point of helium-I? D.Can He sublime? E.Which liquid phase of helium is more dense?

The characteristics of superfluid helium as a technical coolant, which derive from its specific transport properties, are presented with particular reference to the working area in the phase...

By contrast, the thermal conductivity of solid Ar at room temperature has a pressure dependence of P1.25, while a T−1.37 dependence is observed for solid Ar at 19 GPa.

Thus at 5800 atm, solid Helium is obtained at a temperature as high as 42K. This is the curious property of Helium system that although liquid cannot exist above the critical temperature (5.2K), solid can exist if sufficiently great pressure is applied.