Liquid alloys Zintl phases

General characteristics of alloys such as those presented in Fig. 3.3 have been discussed by Fassler and Hoffmann (1999) in a paper dedicated to valence compounds at the border of intermetallics (alkali and alkaline earth metal stannides and plumbides) . Examples showing gradual transition from valence compounds to intermetallic phases and new possibilities for structural mechanisms and bonding for Sn and Pb have been discussed. Structural relationships with Zintl phases (see Chapter 4) containing discrete and linked polyhedra have been considered. See 3.12 for a few remarks on the relationships between liquid and amorphous glassy alloys. 

Van der Lugt, W. (1996) Polyanions in liquid ionic alloys. In Chemistry, Structure and Bonding of Zintl Phases and Ions, ed. Kauzlarich, S.M. (VCH Publisher, New York), p. 183. 

Smaller tetrel element clusters like the tetrahedral [E4] ions were observed for the first time in the alloy NaPb [38] and are present in AE phases for E = Si to Pb and A = Na-Cs. Although these phases are not soluble, ammoniates of [Pb4]" have been obtained from liquid ammonia solutions of the binary phase RbPb [39]. The Zintl phases Ai2Sii7 (A = K, Rb, Cs) and KgRb6Sii7, which in the solid state contain [Si4]" and [Sig]" anions in the ratio 2 1, readily dissolve in liquid ammonia, and recently it has been shown that both cluster anions [Si4]" [37] and [Sig]" [40] are retained in solution. Corresponding pentel element clusters in bulk solids are [Pn7] and [Pnn] (Table 1). 

Nowadays this important compound can be easily prepared on a scale up to 200 g when an emulsion of white phosphorus in 1,2-dimethoxyethane is treated vrith liquid sodium-potassium alloy and excess chlorotrimethylsilane is added to the suspension of the hitherto scarcely characterized Zintl phases Na3P and K3P, respectively. With decreasing yield the tris(trimethylsilyl) derivatives of arsane [3], stibane [4], and bismuthane [5] have also been obtained in the same way (Eq. 1). Meanwhile, hesitation to handle dangerous sodium-potassium alloy or white phosphorus led to the development of similar methods to prepare the phosphane [6,7]. 

We shall first review the basic principles of VASP and than describe exemplary applications to alloys and compounds (a) the calculation of the elastic and dynamic properties of a metallic compound (CoSiz), (b) the surface reconstruction of a semiconducting compound (SiC), and (c) the calculation of the structural and electronic properties of Ki Sbi j, Zintl-phases in the liquid state. 

Recently, we and others demonstrated that appropriate germanide Zintl clusters in non-aqueous liquid-crystalline phases of cationic surfactants can assemble well-ordered mesostructured and mesoporous germanium-based semiconductors. These include mesostructured cubic gyroidal and hexagonal mesoporous Ge as well as ordered mesoporous binary intermetallic alloys and Ge-rich chalcogenide semiconductors. 

Zintl, E., J. Goubeau, and W. Z. Dullenkopf. Metals and alloys 1. Salt-hke compounds and intermetallic phases of sodium in liquid atmnonia. Z. Phys. Chem., Abst. A 154 (1931) 1. 

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