Mixed single crystals

E. G. Chernevskaya, The Hardness of Mixed Single Crystals of the CaF2 Type, Sov. Jour. Opt. Tech., 33,346 (1966). 

The complexes [(n-C4H9)4N]2[MS4C4(CN)4], where M = Co, Ni, Cu, and Rh are isomorphous, and mixed single crystals can be grown very easily using the acetone-isobutyl alcohol solvent pair and only slight modifications of the recrystallization procedure. 

Similar conclusions were drawn by Blanzat et al. (1984) who studied TbxLai xP50i4, EuxLai xP50i4 and mixed single crystals TbxEui xP50i4 under pressure. By selective excitation of the 5D4 multiplet of Tb3+ the luminescence of Eu3+ could be observed due to an efficient Tb3+ -> Eu3+ energy transfer. Under pressure the lifetime of the Eu3+ luminescence decreased which was interpreted by a weak back-transfer from Eu3+ to Tb3+ due to the increased overlapping of the 5D4 multiplet of Tb3+ with the 5D2 multiplet of Eu3+. 

Montgomery et al. (1988) have reported that in systems in which attempts were made to prepare alloys of /3-(ET)2l3 with jS-(PT)2l3 (PT = 3-XI) they apparently obtained single crystals of (ET)2l3 which were in fact mixtures of a and p forms. The phenomenon in this system was initially detected and then confirmed by ESR measurements, which were subsequently used to develop a quantitative procedure for the determination of the polymorphic composition of such mixed single crystals . There are other scattered reports in the literature of the phenomenon (e.g. Freer and Kraut 1965), which has been termed composite crystals and has been discussed in detail by Coppens et al. (1990) and Fryer (1997). 

Figure 19 Integrated absorption curves for Br magnetic resonance in a series of mixed single crystals (l-c)KBr-cNaBr. From Ref. 158. Reproduced by permission of the Institute of Pure and Applied Physics.

Fig. J2.S5.A EPR hyperfine structure of a mixed single crystal of K2[TcCl6]/K2(PtCl,] at 1.7 K and (111 -dircction of the magnetic field [-319].

Isac, J. and Ittyachen, M. A. Growth and characterization of rare-earth mixed single crystals of samarium barium molybdate. Bulletin of Materials Science, 5(4), 349-353(1992). 

Beginning in 1968,Tasumi and Krimm (103) undertook a series of experiments using a mixed crystal infrared spectroscopy technique. Mixed single crystals of protonated and deuterated polymer were made by precipitation from dilute solution. The characteristic crystal field splitting in the infrared spectrum was measured and analyzed to determine the relative locations of the chain stems of one molecule, usually the deuterated portion, in the crystal lattice. The main experiments involved blending protonated and deuterated polyethylenes (104-106). 

A large number of ordered surface structures can be produced experimentally on single-crystal surfaces, especially with adsorbates [H]. There are also many disordered surfaces. Ordering is driven by the interactions between atoms, ions or molecules in the surface region. These forces can be of various types covalent, ionic, van der Waals, etc and there can be a mix of such types of interaction, not only within a given bond, but also from bond to bond in the same surface. A surface could, for instance, consist of a bulk material with one type of internal bonding (say, ionic). It may be covered with an overlayer of molecules with a different type of intramolecular bonding (typically covalent) and the molecules may be held to the substrate by yet another fomi of bond (e.g., van der Waals). 

The next step was then to simulate, a four layer CuaPt overlayer on the (100) surface of the platinum substrate. The first layer w as taken to he pure copper, as was found in the experiment, while the second was a mixed copper-platinum, the third a copper and the fourth again a mixed layer. The fifth and all other layers were pure platinum. For the alloy overlayer the same potentials as for the CuaPt single crystal w ere used, and the potential of pure platinum for the substrate. 

Similar to the mixed-halide (Cl, I) 6-13 system, where more chlorine-rich reactions produced a new structure type, materials with an unprecedented zirconium cluster structure are obtained in the Na-Zr-(C1/I)-B system (also with. other cations, see below), when larger Cl/I ratios are used than above. Compounds characterized are Na[(Zr6B)(Cl,I)i4] and Ao.5[(Zr6B)(Cl,I)i4] (with A = Ca, Sr, Ba) [25, 26]. Single crystals of the cubic Na[(Zr6B)Clio.94(i)l3.o6] and... 

The crystal of 2 OPr recrystallized from EtOH/H20 solution, and the mixed crystal of the same ethyl and propyl cinnamate derivatives (2 OEt and 2 OPr), on photoirradiation for 2h at room temperature with a 500 W super-high-pressure Hg lamp, afforded the highly strained tricyclic [2.2] paracyclophane (2 OEt-2 OPr-cyclo) crystal quantitatively (Maekawa et ai, 1991b). A crystal structure analysis was carried out of a single crystal of the complex of 2 OEt-2 OPr-cyclo with HFIP (recrystallization solvent) in a 1 2 molar ratio. Fig. 13 shows the molecular structure of 2 OEt-2 OPr-cyclo viewed along the phenylene planes. The short non-bonded distances and deformation of the benzene rings, as seen in Fig. 13, are common to those of [2.2] paracyclophanes, as previously reported (Hope et ai, 1972a,b). 

---