Researchers Glimpse Distortions in Atomic Structure of Materials
For Immediate Release
Researchers from North Carolina State University are using a technique they developed to observe minute distortions in the atomic structure of complex materials, shedding light on what causes these distortions and opening the door to studies on how such atomic-scale variations can influence a material’s properties.
Researchers have known for years that the properties of complex materials, such as alloys, are influenced by how the material’s component atoms are organized – i.e., where the atoms fit into the material’s crystal structure. But the devil was in the details.
“We knew where the atoms were on average, but we also knew that there were variations in a material – there can be significant displacements, where atoms don’t fit into that average pattern,” says Dr. Doug Irving, an associate professor of materials science and engineering at NC State and co-author of a paper describing the new work.
“However, detecting these distortions required indirect methods that could be difficult to interpret, so we couldn’t fully explore how a material’s atomic structure affects its properties,” says Dr. James LeBeau, an assistant professor of materials science and engineering at NC State and corresponding author of a paper describing the new work.
“Now we’ve come up with a way to see the distortions directly, at the atomic scale,” LeBeau says. “We can create a precise map of atomic organization, including the distortions, within a material. Not only which atoms fit into the structure, but how far apart they are, and how distortions in the structure are related to the chemistry of the material.”
The work builds on a technique LeBeau developed called旋转扫描透射电子显微镜（旋转茎）。
为了测试该技术并了解有关结构扭曲和化学键之间联系的更多信息，研究人员研究了一种称为Lanthanum畸形氧化铝氧化铝（LSAT）的复杂材料。他们之所以选择LSAT，是因为材料内化学键的性质存在显着差异。
“It’s a mess,” LeBeau says. “We didn’t know how the complexity of those bonds influenced structural distortions, and we wanted to see if revolving STEM would give us any insights.”
它做了。
研究人员发现，在LSAT的原子结构中固定腺体和锶的化学键较弱，使其更容易受到化学环境中小小的变化的推动或拉动。
“We never would have been able to directly see the extent of that variation before,” LeBeau says.
“既然我们可以看到这些微妙的扭曲，并知道导致它们的原因，下一步是开始工作以了解这些结构差异如何影响特定的特性。最终，我们希望通过操纵这些原子扭曲来使用这些知识来量身定制材料的性质。”
The paper, “直接观察的媒体ted lattice distortions in complex oxide solid solutions,” was published online Feb. 13 inApplied Physics Letters. Lead author of the paper is Dr. Xiahan Sang, a postdoctoral researcher at NC State. The paper was co-authored by Everett Grimley and Changning Niu, Ph.D. students at NC State. The work was supported by the National Science Foundation under grant number DMR-1151568.
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Note to Editors:The study abstract follows.
“在复杂氧化物固体溶液中直接观察电荷介导的晶格失真”
Authors: Xiahan Sang, Everett D. Grimley, Changning Niu, Douglas L. Irving, and James M. LeBeau, North Carolina State University
Published: Feb. 13,Applied Physics Letters
DOI：10.1063/1.4908124
Abstract:Using aberration corrected scanning transmission electron microscopy combined with advanced imaging methods, we directly observe atom column specific, picometer-scale displacements induced by local chemistry in a complex oxide solid solution. Displacements predicted from density functional theory were found to correlate with the observed experimental trends. Further analysis of bonding and charge distribution were used to clarify the mechanisms responsible for the detected structural behavior. By extending the experimental electron microscopy measurements to previously inaccessible length scales, we identified correlated atomic displacements linked to bond differences within the complex oxide structure.
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