CBED and ALCHEMI investigation of local symmetry and Al, Si ordering in K-feldspars

摘要: CBED (convergent beam electron diffraction) and ALCHEMI (atom location by channelling enhanced microanalysis) have been used to determine the symmetry Al-order parameter 2t 1 within homogeneous regions (of order of 100 nm in diameter) high sanidine low microcline. The results are excellent agreement with those obtained on same crystals from X-ray measurements average T-O bond lengths. In view this agreement, were then applied an orthoclase a well-developed tweed microstructure. indicate that specimen is partially ordered triclinic. lattice modulations involve values γ* range 90°<γ*<90.5°, correspondingly small variations about value 0.67.