Doping alkali metal

For the alkali metal doped Cgo compounds, charge transfer of one electron per M atom to the Cgo molecule occurs, resulting in M+ ions at the tetrahedral and/or octahedral symmetry interstices of the cubic Cgo host structure. For the composition MaCgg, the resulting metallic crystal has basically the fee structure (see Fig. 2). Within this structure the alkali metal ions can sit on either tetragonal symmetry (1/4,1/4,1/4) sites, which are twice as numerous as the octahedral (l/2,0,0) sites (referenced to a simple cubic coordinate system). The electron-poor alkali metal ions tend to lie adjacent to a C=C double... 

The TID design proposed Patterson consists of an alkali metal doped cerwlc cylinder, containing an embedded heater surrounded by a cylindrical collector electrode [100]. The ceramic thermionic emitter is biased at a negative potential with respect to the collector electrode, and it is heated to a surface temperature of 400-800 C, depending on the mode of detection. The response of the detector to different elements depends on the electronic work function of the thermionic surface (i.e., the... 

A. F. Carley, S. D. Jackson, J. N. O Shea and M. W. Roberts, Oxidation states at alkali-metal doped Ni(110)-O surfaces, Phys. Chem. Phys., 2001, 3, 274. 

The reaction of 2-propanol to propanone and propene over a series of alkali-metal-doped catalysts with use of microwave irradiation has been studied by Bond et al. [90], The nature of the carbon support was shown to affect the selectivity of the catalyst. Under microwave irradiation the threshold reaction temperature (i. e. the lowest temperature at which the reaction proceeded) was substantially reduced this was explained in terms of hot spots (Sect. 10.3.3) formed within the catalyst bed. 

In contrast to carbon, which forms structures derived from both sp2 and sp3 bonds, silicon is unable to form sp2 related structures. Since one out of four sp3 bonds of a given atom is pointing out of the cage, the most stable fullerene-like structure in this case is a network of connected cages. This kind of network is realized in alkali metal doped silicon clathrate (19), which were identified to have a connected fullerene-like structure (20). In these compounds, Si polyhe-dra of 12 five-fold rings and 2 or 4 more six-fold rings share faces, and form a network of hollow cage structures, which can accommodate endohedral metal atoms. Recently, the clathrate compound (Na,Ba), has been synthesized and demonstrated a transition into a superconductor at 4 K (21). The electronic structure of these compounds is drastically different from that of sp3 Si solid (22). 

Since alkali metal doped fullerenes are conductors, and low-temperature superconductors, one wonders if the curved polynuclear hydrocarbons might exhibit a similar behavior. 

In the case of oxide catalysts or alkali metal-doped oxide catalysts, basic surface sites can be generated by decarboxylation of a surface metal carbonate exchange of hydroxyl hydrogen ions by electropositive cations thermal dehydroxylation of the catalyst surface condensation of alkali metal particles on the surface and reaction of an alkali metal with an anion vacancy (AV) to give centers (e.g., Na + AV — Na + e ). 

VIII. Alkali Metal-Doped Alkaline Earth Metal Oxides... 

The preparation of alkali metal-doped alkaline earth metal oxides can generally be carried out by two different methods ... 

As stated above, a second route for the preparation of alkali-doped alkaline earth metal oxides is impregnation with aqueous solutions of alkali metal salts or hydroxides. As shown by Kijenski et al. (242), the resultant alkali metal-doped... 

Hur et al. (252,277,278) reported the use of alkali metal-doped MgO to catalyze the synthesis of acrylonitrile and propionitrile (278). Acrylonitrile is an important chemical, especially in the polymer industry it is generally synthesized by the ammoxidation of propene catalyzed by multicomponent bismuth molybdates (279). An alternative method of synthesis of acrylonitrile is the reaction between methanol and acetonitrile (Scheme 42). 

The discovery of superconductivity [105] in alkali metal doped attracted the attention of a broad cross-section of the scientific community. The composition of the first alkali metal doped fullerene was determined to be [106,107]. In this compoimd, the transition to a superconducting state occurs at = 19.3 K [106]. In a short time, a large variety of alkali metal fullerides M Cgo have been synthesized and studied with respect to their solid-state properties [1, 106-114]. Thereby, the stoichiometries of as well as the alkali metal with M = Na, K, Rb, Cs have... 

Alkali metal doping of Cjq is also possible by solution-phase techniques [1,118-121]. K CgQ and Rb CgQ containing small fractions of the superconducting M3C50 phases were prepared by allowing toluene solutions of Cjq to react with the alkali metal [118, 119]. During the reaction, the alkali metal fullerides form a black precipitate. In another example, sonication of a solution of Cjq and excess potassium in TMEDA yields K3C5q(THF)j4 with a defined stoichiometry [104],... 

MitsuhashiR, Suzuki Y, Yamanari Y, MitamuraH, KambeT, BcedaN, OkamotoH, Fujiwara A, Yamaji M, Kawasaki N, Maniwa Y, Kubozono Y (2010) Superconductivity in alkali-metal-doped picene. Nature 464 76-79... 

Haddon RC, Hebard AF, Rosseinsky MJ, Murphy DW, Duclos SJ, Lyons KB, Miller B, Rosamilia JM, Fleming RM, Kortan AR, Glarum SH, Makhija AV, Muller AJ, Eick RH, Zahurak SM, Tycko R, Dabbagh G, Thiel FA (1991) Conducting films of Cgo and C70 by alkali-metal doping. Nature 350 320-322... 

Fig. 1 H uckel energy levels of Ceo together with one component of the triply degenerate ti set of molecular orbitals that become populated upon alkali metal doping or electrochemical reduction.

Haddon, R. C. 1992 Electronic structure, conductivity, and superconductivity of alkali metal doped C60. Acc. Chem. Res. 25, 127-133. 

Electron Correlation and Jahn-Teller Effect in Alkali-Metal-Doped C60... 

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