One-Dimensional Pencil Disorder Discovered for a Class of Intermetallic Compounds
Leonid A. Bendersky
viations of atoms from an average crystal structure caused by structural distortions, chemical ordering, or the presence of defects cause diffuse intensity in scatteringexperiments. The diffuse scattering is usually difficult to detect by x-ray or neutron diffraction, but it is readily observed in electron diffraction. Recently, scientistsat NIST discovered an unusual planar diffusescattering for a group of intermetallic compounds, te-tragonal Zr9M11 (M = Pd, Pt, and Ni) and hexagonal Co3Y4, by using transmission electron microscopy. The near two-dimensional intensity planes are parallel to each other, and the inter-planar distance is incommensuratewith fundamental translations of the averagecrystal structure. By combining electron microscopy with powder neu-tron diffraction, the researchers determined that these compounds could be described as having a host periodic structure, but with one-dimensional structural channels.The channels are filled with strings of atoms, and a one-dimensional arrangement of the atoms along the strings has a periodicity that differs from the host structure. There is a weak correlation between the relative positions (phase) of the strings, i.e., the strings are largely independent of each other. In previous x-ray diffraction studies the possible existence of such disorderwas proposed in order to explain unusually hightemperature factors; however, the unambiguous demonstration of the phenomenon was presented in this NIST work for the first time. It is possible that the presence of the strings could impose special one-dimensional properties in a three- dimensional crystal.
One-Dimensional Pencil Disorder Discovered for a Class of Intermetallic Compounds, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD
(Accessed February 24, 2024)