UCLA scientists determine method to find 3-D positions of atoms
(Courtesy of Jianwei Miao)
Sept. 24, 2015 9:01 a.m.
Atoms pictured in textbooks depict estimations of their average position in materials, but are not entirely accurate. UCLA scientists discovered a way to precisely determine their location in materials and accurately depict them in 3-D models that shows gaps in groups of atoms.
In a study published on Monday in Nature Materials, researchers used a technique called scanning transmission electron microscopy, or STEM, to scan atoms in tungsten, an element used in incandescent light bulbs.
Jianwei Miao, lead researcher and a physics and astronomy professor, said the team used an electron microscope to scan the atoms before reconstructing them in 3-D. Miao said understanding more accurate positions of the atoms in the 3-D models will allow scientists and engineers to better understand the materials they work with.
According to a UCLA press release, the sample needed to be tilted to reconstruct the image in 3-D, because scientists can only use the electron microscope to scan atoms in two dimensions. The team tilted the sample through a computer 62 times, a process that took about three hours.
To scan the sample, the electron microscope needed to be isolated in a room with no vibrations, so the process would not be disrupted.
“Every image takes about one minute to take,” Miao said. “Then we have to locate a different angle and wait a few minutes because we want to get it accurately.”
X-ray crystallography, which measures how light waves scatter off a crystal, is the most common method used to identify atoms’ locations, according to the press release. However, the method only determines average positions of billions of atoms.
Miao compared crystallographic images of atoms’ positions to an army of soldiers.
“In two dimensions, you can’t identify a missing soldier,” he said. “But with this new method, scientists can precisely see missing atoms in a substance, which are called point defects.”
Point defects can change the properties of a structure. For example, a gap in the atoms of materials used to make an LED light can change its effectiveness, Miao said.
Being able to see atoms in 3-D models can allow scientists and engineers to design new materials and structures, such as aircrafts. Miao said he hopes other researchers will use his methods to learn more about different materials and elements.
Compiled by Alejandra Reyes-Velarde, Bruin senior staff.