Mg NMR

The Mg in the silicate minerals reflects an octahedral site preference, being located predominantly in MgO sites. Various correlations between the Xq values and geometrical distortion factors of the Mg sites in these minerals have been sought 

Another promising relationship with Xq is also related to the octahedral bond angles and involves the shear strain ij within the coordination polyhedra, defined as 

Although the efg effects in these minerals are likely to be more complex than suggested by these simple relationships, they could provide a simple means of tentatively assigning octahedral resonances to specific sites. No satisfactory relationships have been found between the Mg NMR parameters and functions involving the octahedral bondlength (MacKenzie and Meinhold 1994a). 

As the silicate structure is disrupted by the loss of hydroxyl water, the octahedral Mg sites become progressively distorted, as reflected by broadening and intensity loss of the Mg signal, but the Mg remains in octahedral coordination throughout (MacKenzie and Meinhold 1994d). 

The increasing use of lightweight dilute magnesium-aluminium alloys in the automotive industry has led to Mg NMR studies of some of these materials. The Mg NMR spectrum of Mg-6 % A1 is very similar to that of pure Mg apart from a small variation in the chemical shift and a smearing out of the satellite transitions resulting from a distribution of interactions as the A1 substitutes into the framework (Bastow and 

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Overview of practical considerations of experimental approaches for solid-state Mg NMR... 

First-Principles Calculations in Solid-State Mg NMR Applications of Solid-State Mg NMR... 

Key Words Mg NMR, Solid state NMR, Signal enhancement, First-principles calculations, Materials characterisation... 

Besides the use of large volume samples, there are also other "brute force" approaches frequently used since the earlier reports of solid-state Mg NMR, including isotopic enrichment and the use of malefic fields as strong as possible.. 39.42,, 45-52 jg doubt that the increase in the... 

Cq of 2.40MHz, the unoptimised structure calculation gave Cq= 1.86MHz, whereas full geometry optimisation led to a much better calculated value of Cq=2.36MHz. These facts illustrate that the choice of the best structure to be used in calculations of Mg NMR parameters is still an open issue that needs to be addressed case by case. 

Mg-Al alloys and intermetallics have been the focus of many investigations motivated by the interest in these materials due to their industrial use in the manufacture of lightweight components. Mg NMR spectra of Mg-rich alloys are similar to Mg metal. The alloy Mg-6wt% A1 was studied by Bastow and Smith, ° who reported a slight shift of the resonance compared to that foimd in pure Mg metal (/ 16ppm upheld) and a... 

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