To create mountains from the common mineral dolomite, the dolomite must be periodically dissolved.This seemingly paradoxical concept could help eliminate new flaws semiconductor more.
For two centuries, scientists have failed to grow common minerals in the laboratory under conditions under which they would be naturally formed.Currently, a team of researchers from the University of Michigan Hokkaido University A research team in Sapporo, Japan has finally succeeded in doing just that, thanks to a new theory developed from atomic simulations.
Their success solved a long-standing geological puzzle called the “dolomite problem.” Dolomite is an important mineral found in the Italian Dolomites Mountains, Niagara Falls, the White Cliffs of Dover, and the Hoodoos of Utah, where it is extremely abundant in rocks. over 100 million years oldbut almost non-existent in young formations.
The importance of understanding dolomite growth
“If we can understand how dolomite grows in nature, we may learn new strategies for promoting crystal growth in modern technology materials,” said Dr. said Wenhao Sun, who is also the corresponding author of the paper.was announced on science.
Ultimately, the secret to growing dolomite in the lab was to remove defects in the mineral structure as it grew. When minerals form in water, atoms are usually deposited neatly at the edges of the growing crystal surface. However, the growing edge of dolomite consists of alternating rows of calcium and magnesium. In water, calcium and magnesium randomly attach to the growing dolomite crystals, often staying in the wrong places, creating defects that prevent the formation of additional dolomite layers. This disorder significantly slows the growth of dolomite, and it takes 10 million years to create just one layer of ordered dolomite.
Fortunately, these flaws are not fixed. Disorganized atoms are more unstable than properly positioned atoms, so when you wash a mineral with water, it dissolves first. By repeatedly washing away these defects with rain and tides, a dolomite layer is formed in just a few years. Over the course of geological time, piles of dolomite can accumulate.
Advanced simulation technology
To accurately simulate dolomite growth, the researchers needed to calculate how tightly or loosely the atoms would attach to the existing dolomite surface. The most accurate simulations require the energy of all interactions between electrons and atoms within the growing crystal. Such exhaustive calculations typically require vast amounts of computing power, but software developed at UM’s Predictive Structural Materials Science (PRISMS) Center provided a shortcut.
“Our software calculates the energy of some atomic arrangements and extrapolates to predict the energies of other atomic arrangements based on the symmetries of the crystal structure,” said one of the software’s lead developers. said Brian Puchala, associate research scientist at Massachusetts State University. He holds a PhD in materials science and engineering.
This shortcut made it possible to simulate dolomite growth over geological timescales.
“Typically, each atomic step takes more than 5,000 CPU hours on a supercomputer. Now we can perform the same calculation on a desktop in 2 milliseconds,” says the doctoral student in materials science and engineering. said Joonsoo Kim, lead author of the study.
Practical application and testing of theory
Currently, the few areas where dolomite forms are intermittently flooded and then dry out, which fits well with Sun and Kim’s theory. However, such evidence alone was not enough to be completely convincing. Yuki Kimura, a professor of materials science at Hokkaido University, and Tomoya Yamazaki, a postdoctoral researcher in Kimura’s lab, will appear. They used the peculiarities of transmission electron microscopy to test new theories.
“An electron microscope typically uses an electron beam just to image the sample,” Kimura says. “But the beam can also split water, so acid Crystals may dissolve. Normally this would have a negative impact on imaging, but in this case lysis is exactly what we wanted. ”
After placing the small dolomite crystals in a solution of calcium and magnesium, Kimura and Yamazaki gently pulsed the electron beam 4,000 times over two hours to dissolve the defects. After the pulse, dolomite was observed to grow to about 100 nanometers, or about 1/250,000th of an inch. This was only 300 layers of dolomite, but he had never before grown more than five layers of dolomite in the lab.
Lessons learned from the dolomite problem will help engineers produce high-quality materials for semiconductors, solar panels, batteries, and other technologies.
“In the past, crystal growers who wanted to create defect-free materials tried to grow them very slowly,” Sun says. “Our theory shows that we can rapidly grow defect-free materials if we eliminate defects periodically during growth.”
Reference: “Dissolution enables dolomite crystal growth at near ambient conditions”, Joonsoo Kim, Yuki Kim, Brian Puchala, Tomoya Kawasaki, Udo Becker, Wenhao Sun, November 23, 2023. science.
DOI: 10.1126/science.adi3690
This research was funded by the American Chemical Society PRF New Doctoral Investigator Grant, the U.S. Department of Energy, and the Japan Society for the Promotion of Science.