Alkali metal halides monomers

Somewhat to our surprise, we have been unable to find reference to any published attempt to calculate these bond energies of the gaseous dihalides on the basis of the Bom-Lande lattice energy model. We have therefore carried out such calculations at a level that reproduced the bond energies of the alkali metal halide monomers with an average deviation from the experimental values of 8%. All calculations were carried out on linear XMX structures. The ratio between these calculated values and their experimental counterparts are listed in the last column of Table 2. 

While this is probably the best reference that can be found, it seems important to remark that ionic radii depend on the environment surrounding the ions, that is, on the force field in which the ions lie. Studies of the ion pairs formed in alkali metal halide vapour show that the distance between anion and cation may be 20 % smaller than the interionic distance for the same pair in the crystal. Dimers in the vapour phase have a distance between anion and cation which is intermediate between that in the monomer and that in the crystal. When an alkali salt melts, the first-neighbour distance may decrease up to... 

Alkali halide vapor consists mainly of monomers and dimers. As stated in Sec. 1-22, Linevsky developed a technique to isolate these monomers and dimers, produced at high temperature, in inert gas matrices. This technique has been used extensively to study the infrared spectra and structures of a number of inorganic salts. Some references on metal halide dimers are LiF)2. (LiCOz, (LiBr)2, and (NaX)2 (X = F, Cl, Br, and 1). These dimers are known to be cydic-planar (02 ). On the other hand, (T1X)2(X — F and Cl) are linear and symmetrical (Doo X-Tl-Tl-X). Such structures have been well known for (HgX)2 (X = C1, Br, and 1). The dimer LiO)2 is also cyclic-planar. However, (Nbl)2 is frans-planar (C2J,) in a Nj matrix but takes the cis structure upon complex formation with the Cr(CO)s group. ... 

Type A copolymers and terpolymers have been prepared by copolymerizing vinyl pyridinium halides with alkali metal salts of sulfonate comonomers including vinylsulfonate, 2-acrylamido-2-methyl propane sulfonate, and p-styrene sulfonate (15-19). Methacrylamidopropyl-trimethyl ammonium chloride and p-styrene sulfonate have been terpolymerized with the hydrophilic monomer acrylamide (20,21). Type A copolymers and terpolymers have also been prepared from microemulsions of sodium 2-acrylamido-2-methyl-l-propanesulfonate and [2-(methacryloyloxy)ethyl]trimethylammonium chloride (22-25). 

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