Location of 23,000 single atoms seen for first time

Scientists have for the first time seen the exact locations of more than 23,000 atoms in a particle that is small enough to fit inside the wall of a single cell.
Researchers led by University of California, Los Angeles (UCLA) in the US used a scanning electron microscope to examine a particle that was made of iron (Fe) and platinum (Pt) and only 8.4 nanometres across.
"At the nanoscale, every atom counts," Michael Farle, a physicist at the University of Duisburg-Essen in Germany.
"For example, changing the relative positions of a few Fe and Pt atoms in a FePt nanoparticle dramatically alters the particle's properties, such as its response to a magnetic field," said Farle.

Getting such an accurate picture may help materials scientists in future to create nanometre-size structures for applications such as hard drives.
Makers of hard drives want to fabricate tiny, near-perfect crystals so that they can be easily magnetised and will hold a magnetic field for a long time, Ercius noted.

Knowing each atom's exact location would also allow scientists to predict how a crystal might grow, 'Live Science' reported.
A beam of electrons is passed over the surface of an object using a scanning electron microscope to create an image. That allows researchers to see even small details of tiny bits of material like crystals and protein molecules.

The iron-platinum nanoparticles are a kind of irregular crystal. However, the ordinary scanning method would not work as well for them, because the atoms are arranged in unique and slightly irregular ways.
The researchers had to find a new way to use the electron microscope.
They altered the way the sample was prepared. Instead of leaving it in place, they put it on a special base that let them rotate and tilt their particle of iron and platinum, changing its orientation slightly after each "snapshot" with the electron beam.
The varying orientations produced different patterns of scattering, which were picked up on a detector similar to the ones in digital cameras, that could be used to calculate the exact positions of the 6,569 iron and 16,627 platinum atoms in the nanoparticle.

The research was published in the journal Nature.