K AlSi

In contrast to the other types of tetrahedron linkage already described, the three-dimensional frameworks commonly exist in a number of entirely different forms which give rise to several quite distinct families of petrologically important minerals. A few silicates have structures based on the frameworks found in the various forms of silica. Thus the structures of kalsilite, K(AlSi)04, and nepheline, Na3K(Al4Si4)016, can be regarded as derived from that of tridymite by the replacement of one-half of the silicon ions by aluminium and the introduction of the appropriate number of alkali ions to restore neutrality. The structures of carnegeite, Na(AlSi)04, and eukryptite, Li(AlSi)04, are similarly related to those of cristobalite and quartz, respectively. It will be noted that in all these minerals aluminium is, of course, always present and that the 0 (Si, Al) ratio is always 2 1. 

The most commonly encountered members of the nepheline-trimerite group are nepheline, KNa3(Al4Si4)026, and kalsilite, K(AlSi)04, or intermediates. The two end members are not isostructural, but both are hexagonal and have a structure based on the tridymite framework. In both, there is much isomorphous Al-for-Si substitution. The change from the nepheline to the kalsilite structure occurs at about 20 to 30 % nepheline. 

MeV Li ion irradiation for AlSi/HfOj/n-Si MOS capacitors prepared at (a) 1, 10, and 100 kHz and (b) 500 kHz and 1 MHz. (From AmcZ. Instrum. Methods Phys. Res. Sect. B, 269(23), Singh, V., Shashank, N., Sharma, S.K., Shekhawat, R.S., Kumar, D., and Nahar, R.K., Frequency dependence studies on the interface trap density and series resistance of HfOj gate dielectric deposited on Si substrate Before and after 50 MeV ions irradiation, 2765-2770. Copyright 2011b, with permission from Elsevier.)... 

P-group (plastic) long chip building ferrous materials, steel K-group nonferrous metals, cast iron, AlSi alloys, plastics, wood... 

The acidity of a series of MCM-41 mesoporous materials has been investigated by microcalorimetry using ammonia adsorption at 423 K [287], giving rise to the following acid strength sequence H-[AlSi]-MCM-41 > [AlSi]-MCM-41 > [FeSi]-MCM-41 > [LaSi]-MCM-41. 

Nigam, S., Majumder, C., 8c Kulshreshtha, S. K. (2004). Structural and electronic properties of Si , Sin, and AlSi " (n = 2-13) clusters theoretical investigation based on ab initio molecular orbital theory. Journal of Chemical Physics, 121(16), 7756-7763. 

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