The left column is a set of experimental electron diffraction patterns on the <001>, <100>, and <110> zone axes (top to bottom). The rightt side is the corresponding set of multislice simulated patterns based on a model invoving chemical modulation of the Cr substitution for Hg. This modulation is seen in the <110> zone axis pattern, is incommensurate, and lies along the g 1/4.9 1/4.9 1/2 and the g -1/4.9 1/4.9 1/2 directions.

High resolution electron microscope image along the <110> showing the chemcal modulation. A multislice image simulation is inserted right center. The c-axis is vertical and the micron bar is 2 nm long.

Electron diffraction pattern along the <001> zone axis showing evidence for chemical disorder within the Cr modulation. Due to a Cr homogeniety in the <001> projection the modulation should be forbidden in the zero order Laue zone (ZOLZ) and allowed in the first order Laue zone. projection. However, weak diffuse spots in the ZOLZ (top right inset) located at the forbidden <1/5 1/5/ 0> location indicate that there is disorder in the Cr modulation. The modulated produces sharp spots in the FOLZ (top left inset) indicating the modulation is well orderded in c-axis.

E-mail:brad.storey@anl.gov