In general, when crystals are grown, atoms first come together in tiny clusters. This process is referred to as nucleation.
However, the very understanding of how this atomic order occurs from the irregularity of irregularly moving atoms has hampered researchers for a long time.
According to traditional nucleation theory, crystals form one atom at a time, constantly increasing the order rate. New analyzes have also noted a two-step circulating process where a high-energy mobile structure first forms and this structure then transforms into a stable crystal.
However, according to an international research group, with the Lawrence Berkeley National Laboratory (Berkeley Lab) in the Department of Energy, the story itself is much more complex.
The researchers’ conclusions have now emerged that, instead of coming together in a continuous way or providing a single irreversible transition, there will be gold atoms instead of organizing with them. themselves, separating them, recycling them, and then rearranging them several times before accepting an ordered and stable crystal. The results of the study were recently published in the Science iris.
For the first time, the researchers were able to observe this fast and adaptable nucleation process using an electron electron microscope. Their study offers a solid understanding of the early stages of several growth processes, such as nanoparticle formation and thin film deposition.
As scientists try to control matter at smaller blades to extract new materials and tools, this study helps us to understand how some crystals.
Peter Ercius, Associate Research Author and Staff Scientist, Molecular Furnace, Lawrence Berkeley National Laboratory
According to the team ‘s traditional understanding, as soon as the crystals reach a certain size, they do not return to an unstable, chaotic state.
Won Chul Lee, one of the professors leading the study, explained this phenomenon in this way: if every atom is seen as a Lego brick, then instead of building a house using one bricks at the same time, the bricks always fit together and separate again so that they are strong enough to stay together. But after the foundation is laid, additional bricks can be added without disturbing the whole structure.
In this case, the team was only able to see the unstable structures due to the speed of the recently designed detectors on TEAM I – one of the strongest electron microscopes in the world. The experiments were conducted by a group of in-house experts from the National Center for Electron Microscope in the Molecular Furnace of the Berkeley Lab.
The researchers used a TEAM I microscope and recorded live resolution images at rates of up to 625 frames per second, which is very fast for an electronic microscope, and about 100-fold faster than earlier analyzes.
Individual gold atoms were observed as they became crystals, disintegrated into individual atoms, and then regenerated into several crystal arrangements before becoming stable at the end. over there.
Slower views would miss this fast-paced, adaptable process and just see a blur instead of the transitions, which explains why this nucleation behavior has never been seen before..
Peter Ercius, Associate Research Author and Staff Scientist, Molecular Furnace, Lawrence Berkeley National Laboratory
The philosophy behind this miracle is that the formation of crystals is an exothermic process – in other words, it releases energy. In fact, the precise energy released when atoms attach to the small nuclei can increase the local “temperature” and thus melt the crystal.
In this way, the initial process of crystal formation works against itself, alternating between disorder and order several times before building a nucleus that is stable enough to withstand the heat.
To test this understanding of their experimental ideas, the researchers performed a number of binding reactions between a nanocrystal and a hypothetical gold atom.
Scientists are now designing detectors that are relatively faster and could be used to capture the process at higher speeds. This approach may help them to determine whether additional features of nucleation are hidden in the atomic disorder.
The researchers also hope to find similar movements in several atomic systems to see if this latest discovery reflects a common normalization process.
From a scientific point of view, we discovered a new principle of crystal rotation process, and tested it experimentally.
Jungwon Park, Principal study author, Seoul National University
Berkeley Lab led the collaborative study in collaboration with Hanyang University of South Korea, Seoul National University, and the Institute for Basic Science.
The Molecular Furnace is a DOE Science Office user facility.
The study was mainly funded by the Korea National Research Foundation. The research work at the Molecular Furnace was financially supported by the U.S. Department of Energy’s Office of Science, Office of Basic Energy Sciences.
Additional funding was provided by the Institute for Basic Science (Korea), the U.S. National Science Foundation, and the Samsung Science and Technology Foundation.
Scientists and colleagues at Berkeley Lab took advantage of one of the world’s finest microscopes – the Molecular Furnace’s TEAM I electron microscope – to see how individual gold atoms formed themselves into crystals on top of graphene . The research team observed how groups of gold atoms formed and separated many times, trying different arrangements, before finally becoming stable. Video Credit: Lawrence Berkeley National Laboratory.
Magazine Information:
Jeon, S., et al. (2021) Reversible order-to-order transitions in atomic crystal rotation. Science. doi.org/10.1126/science.aaz7555.
Source: https://newscenter.lbl.gov/