Printer Friendly

One-dimensional "pencil" disorder discovered for a class of intermetallic compounds. (General Developments).

Deviations of atoms from an average crystal structure caused by structural distortions, chemical ordering, or the presence of defects cause diffuse intensity in scattering experiments. The diffuse scattering is usually difficult to detect by x-ray or neutron diffraction, but it is readily observed in electron diffraction. Recently, scientists at NIST discovered an unusual planar diffuse scattering for a group of intermetallic compounds, tetragonal [Zr.sub.9][M.sub.11] (M = Pd, Pt, and Ni) and hexagonal [Co.sub.3][Y.sub.4], by using transmission electron microscopy. The near two-dimensional intensity planes are parallel to each other, and the inter-planar distance is incommensurate with fundamental translations of the average crystal structure.

By combining electron microscopy with powder neutron 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 disorder was proposed in order to explain unusually high temperature 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.

CONTACT: Leonid Bendersky, (301) 975-6167; leonid. bendersky@nist.gov or Judith Stalick, (301) 975-6223; judith.stalick@ nist.gov.
COPYRIGHT 2002 National Institute of Standards and Technology
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2002, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

 Reader Opinion

Title:

Comment:



 

Article Details
Printer friendly Cite/link Email Feedback
Publication:Journal of Research of the National Institute of Standards and Technology
Geographic Code:1USA
Date:Jul 1, 2002
Words:263
Previous Article:New pulsed laser deposition technique speeds search for high-tech thin films. (General Developments).
Next Article:NIST produces two new wavelength calibration standards for the wavelength division multiplexing L-band. (Standard Reference Materials).
Topics:


Related Articles
A flash in the crystalline pan.
Discovering the colorful new world of tin.
Frothy physics: scrutinizing the laws of suds.
Avalanches in a magnetic froth.
Antimony in aluminum scrap.
Revisiting intermetallic superconductors.
WIRED FACES.
NIST/FIZ-KARLSRUHE PARTNERSHIP TO IMPROVE THE INORGANIC CRYSTAL STRUCTURE DATABASE FOR MATERIALS RESEARCH.
Let's play chess.
Electron diffraction using transmission electron microscopy.

Terms of use | Copyright © 2014 Farlex, Inc. | Feedback | For webmasters