Compressed Xenon

The electronic bands of an infinite crystal can cross as a function of some parameter (pressure, concentration etc.). If one treats the e /r,2 term of the electron repulsion correctly, one sees that the crossing transition of the two bands is a first-order phase transition, between the metallic and insulating states. This transition was predicted by Mott in 1946 and has carried his name ever since. In fact, the original Mott criterion does not predict such a transition for Hg, but the criterion was derived for monovalent atoms. For divalent mercury it should not be applicable. Also the semiempirical Herzfeld criterion, which was very successful in predicting the insulator to metal transition in compressed xenon, predicts bulk Hg to be non-metallic. All this seems to imply that Hg is a rather special case. 

Ross M 1968 Shock compression of argon and xenon. IV. Oonversion of xenon to a metal-like state Phys. Rev. 171 777... 

Values extracted and in some cases rounded off from ttose cited in RaLinovict (ed.), Theimophysical Propeities of Neon, Ai gon, Kiypton and Xenon, Standards Press, Moscow, 1976. Ttis source contains values for tte compressed state for pressures up to 1000 bar, etc. t = triple point. Above tbe sobd line tbe condensed phase is solid below it, it is liquid. Tbe notation 5.646. signifies 5.646 X 10 . At 83.8 K, tbe viscosity of tbe saturated liquid is 2.93 X 10 Pa-s = 0.000293 Ns/ui . Tbis book was published in English translation by Hemisphere, New York, 1988 (604 pp.). 

The definition of w makes its value zero for argon, krypton, and xenon, and experimental data yield compressibility factors for all three fluids that are correlated by the same curves when Z is represented as a function of Tr and Pr. Thus the basic premise of the three-parameter theorem of corresponding states is that all fluids having the same value of w have the same value of Z when compared at the same Tr and Pr. 

Figure 9.8. Possible structures for argon, krypton and xenon adsorbed in registry with graphite. Dotted unit cell Xe linearly expanded by (4.91 -4.40)/4.40 = 11.6%. Dashed unit cell Xe linearly compressed by (4.40-4.26)/4.26 = 3.2%. Kr expanded by (4.26 - 4.07)/4.07 = 4.7% and Ar expanded by (4.26- 3,85)/3.85 = 10.6% (reproduced courtesy of Larher, 1974).

The mobility in krypton is quite high at all pressures and there is only a shallow minimum in this case. The data shown in Fig. 4 are for 20°C, which is well above the critical temperature. The minimum becomes lower at lower temperatures but not as low as in xenon. The electron mobility in krypton is also reasonably well represented by Eq. (4) when the adiabatic compressibility is used. ... 

Hydrates and deuterates have, however, been made by compressing the inert gases with water and DgO. Those formed by the heavier elements are the most stable and contain six HgO or DgO molecules to one inert gas atom, as in Xe.GHgO where the xenon atom is evidently polarised by the strong dipole. This thesis is supported by the increase in water-solubility down Gp. O ... 

A supercritical fluid is defined as a substance above its critical temperature (Tc) and critical pressure (Pc). The critical point represents the highest temperature and pressure at which the substance can exist as a vapor and liquid in equilibrium (Tables 3 and 4). Supercritical fluids are highly compressed fluids that combine properties of gases and liquids in a synergistic manner. Fluids such as supercritical xenon, ethane, and carbon dioxide (CO2) offer a range of unusual chemical possibilities in both synthetic and analytical chemistry. 

Piperazine 2 is also highly synergistic with commercial UV absorbers, as shown in 20 mil-thick compression-molded polypropylene samples aged in a xenon Weather-Ometer. 

---