SHORT-RANGE ORDER IN MINERALS: AMPHIBOLES

Defects and Short-range Order in Nepheline Group Minerals: a Silicon-29 Nuclear Magnetic Resonance Study

29Si magic-angle spinning nuclear magnetic resonance (NMR) spectra are presented for seven crystalline phases of the nepheline group: natural nephelines from a plutonic environment (Bancroft, Ontario) and a volcanic deposit (Mt. Somma, Italy), kalsilite, synthetic pure Na nepheline, carnegieite, and two samples of orthorhombic KA1SiO4. In all phases, nearly all of the Si sites have four A1 neig...

Short-range order in ternary aUoy semiconductors

Atom arrangements in IH-V ternary aHoy semiconductors are discussed using a thermodynamic analysis in which the elastic strain caused by mixing is considered as the mixing enthalpy. In calculating the strain energy, both bond-stretching and bond-angl.e distortion are taken into account, and Martin's microscopic elastic constants are used. The results show that there is a preference for ordering...

Short-range order of compressed amorphous GeSe2

The structure of amorphous GeSe2 (a-GeSe2) has been studied by means of a combination of two-edges X-ray absorption spectroscopy (XAS) and angle-dispersive X-ray diffraction under pressures up to about 30 GPa. Multiple-edge XAS data-analysis of a-GeSe2 at ambient conditions allowed us to reconstruct and compare the first-neighbor distribution function with previous results obtained by neutron d...

Short range smectic order driving long range nematic order: example of cuprates.

We present a model for describing the combined presence of nematic and 'smectic' or stripe-like orders seen in recent scanning tunneling microscopy (STM) experiments on cuprates. The smectic order is treated as an electronic charge density wave with an associated Peierls distortion or a 'Pomeranchuk wave'. This primary order is restricted to nanoscale domains by disorder effects, while the seco...

Spatial variation of short-range order in amorphous intergranular complexions