Scientists finally succeeded in growing dolomite in the laboratory by eliminating structural defects during growth

For 200 years, scientists have failed to grow common minerals in the laboratory under conditions under which they would be considered naturally formed. Now, a research team from the University of Michigan and Hokkaido University in Sapporo, Japan, has finally succeeded, thanks to a new theory developed from atomic simulations.

Their success solved a long-standing geological puzzle called the “dolomite problem.” An important mineral in the Italian Dolomites, Niagara Falls, the White Cliffs of Dover, and Utah’s Hoodoo, dolomite is extremely abundant in rocks. over 100 million years oldbut almost non-existent in young formations.

“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, corresponding author of the published paper.Today is 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.

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 configurations and extrapolates to predict the energies of other configurations based on the symmetries of the crystal structure,” said one of the software’s lead developers. said Brian Puchala, associate research scientist in UM’s materials division. science and engineering.

This shortcut made it possible to simulate dolomite growth over geological timescales.

“Each atomic step typically 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.

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. “However, the beam can also split water, thereby producing acids that cause the crystals to dissolve. Normally this would have a negative effect on image processing, but in this case the dissolution is exactly what we want. It was there.”

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 said. “Our theory shows that defect-free materials can be grown quickly if defects are periodically dissolved and removed during growth.”