Argon crystal structure

Fig. 1. The crystal structure of a hydroquinone clathrate according to Palin and Powell. 8 The balls inside the transparent spheres represent argon atoms encaged in the cavities formed by the two interpenetrating lattices, (photograph kindly supplied by Dr. Powell).

Problems 8.1 Fhsm Fig. 8.1 describe the crystal structure of solid argon. 

NEON. [CAS 7440-01-9], Chemical element, symbol Ne, at. no. 10. at. wt. 20 183, periodic table group 18,mp —248,68 C. bp —246.0UC, density 1.204 g/cm3 (liquid). Specific gravity compared with air is 0.674. Solid neon has a face-centered cubic crystal structure. At standard conditions, neon is a colorless, odorless gas and does not form stable compounds with any other element, Due to its low valence forces, neon does not form diatomic molecules, except tn discharge tubes. It does form compounds under highly favorable conditions, as excitation m discharge tubes, or pressure in the presence of a powerful dipole, However, the compoundforming capabilities of neon, under any circumstances, appear to be far less than those of argon ur krypton. No knuwn hydrates have been identified, even at pressures up to 260 atmospheres. First ionizadon potential, 21.599 eV. 

Eu-Ni-Sb. Marchand and Jeitschko (1978) investigated the crystal structure of the EuNi2Sb2 compound (ThCr2Si2 type structure a = 0.43834, c = 1.0664 X-ray powder diffraction). Stoichiometric amounts of the elemental components (Eu, Ni better than 99.5%, Sb better than 99%) were sealed under argon in silica tubes, heated at 920 K for 12 h, followed by 4 h at 1250 K and rapid cooling. The samples were then ground to powder, cold pressed to... 

An early investigation of the TbNiSb compound showed that it had the MgAgAs-type with a = 0.6327 (Dwight, 1974), from an X-ray powder analysis of an alloy arc melted under argon and annealed at 973 K. Pecharsky et al. (1983a) and Hartjes and Jeitschko (1995) confirmed the crystal structure and obtained the lattice parameters as a = 0.6302 and a = 0.6304, respectively, by X-ray powder diffraction. For experimental details, see ScNiSb and LaNiSb respectively. 

Yb-Au-Sb. The LiGaGe type was established for the YbAuSb compound (a = 0.4635, c = 0.7765) by Merlo et al. (1990) by means of powder and single crystal diffraction method on a sample obtained by melting stoichiometric amounts of the components in iron or in tantalum crucibles and arc welded shut under an argon atmosphere. After slow cooling, no further thermal treatments were applied. The purities of the metals were Yb 99.9%, Au and Sb 99.999%. The crystal structure was confirmed by Flandorfer et al. (1997) by X-ray powder diffraction. 

Formation of the energy-band structure of KCl. We start with argon atoms, and then put them in a simple-cubic crystal structure. Protons arc then transferred between neighboring nuclei to form potassium and chlorine ions. 

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