Centuries-Old ‘Dolomite Problem’ Finally Solved

For two centuries, scientists struggled to replicate a common mineral’s natural formation conditions in lab settings. Recently, a collaboration between the University of Michigan and Hokkaido University cracked this puzzle, achieving success by applying a novel theory derived from atomic simulations.

This breakthrough addresses the persistent geological enigma known as the “Dolomite Problem.” Dolomite, crucial in formations like the Dolomite mountains, Niagara Falls, the White Cliffs of Dover, and Utah’s Hoodoos, is abundant in rocks older than 100 million years but notably scarce in younger ones.

“If we decipher how dolomite naturally grows, it could unveil novel techniques to encourage the crystalline growth of modern materials used in technology,” explained Wenhao Sun, the Dow Early Career Professor of Materials Science and Engineering at U-M and the lead author of the paper published in Science.

The breakthrough in growing dolomite in the lab involved rectifying flaws in the mineral’s structure during its growth process.

Geology’s age-old ‘Dolomite Problem’ is solved: dolomite’s growth edge

Typically, when minerals develop in water, atoms adhere neatly to the advancing crystal’s edge. However, dolomite’s growth edge comprises alternating calcium and magnesium rows.

In the water, calcium and magnesium irregularly adhere to the developing dolomite crystal, often occupying incorrect positions, generating flaws that impede further dolomite layers from forming.

This disorder significantly hinders dolomite’s growth, making it an exceedingly slow process, taking up to 10 million years to create just a single layer of ordered dolomite.

Fortunately, these defects are not permanent. When water rinses the mineral, disordered atoms dissolve first due to their instability compared to atoms in the correct positions.

Geology’s age-old ‘Dolomite Problem’ is solved: a dolomite layer

By repeatedly eliminating these defects—such as through rainfall or tidal cycles—a dolomite layer can develop within a few years. Over extended periods, dolomite can accumulate into substantial mountain formations.

For precise simulation of dolomite growth, researchers needed to calculate the attachment strength of atoms to an existing dolomite surface accurately.

This level of accuracy in simulations typically demands immense computing power. However, software developed at U-M’s Predictive Structure Materials Science (PRISMS) Center offered a streamlined approach.

“Our software predicts energies for different atomic arrangements by assessing a few and extrapolating based on crystal structure symmetry,” said Brian Puchala. Software lead and associate research scientist in U-M’s Materials Science and Engineering Department.

Geology’s age-old ‘Dolomite Problem’ is solved: The computational shortcut

The computational shortcut enabled the simulation of dolomite growth across geological time frames.

Previously, each atomic step took over 5,000 CPU hours on a supercomputer. Joonsoo Kim, a doctoral student in materials science and engineering and the study’s primary author, mentioned that a desktop can now complete the same calculation in 2 milliseconds.

Contemporary sites where dolomite sporadically forms—flooded and subsequently dried areas—corroborate Sun and Kim’s theory. However, this evidence alone wasn’t entirely convincing.

Yuki Kimura, a materials science professor at Hokkaido University, and Tomoya Yamazaki, a postdoctoral researcher in Kimura’s lab, corroborated the new theory using an unusual feature of transmission electron microscopes.

“Usually, researchers employ electron microscopes just for imaging samples. However, the electron beam can also split water, generating acid that dissolves crystals. Despite this usually being detrimental for imaging, in this instance, dissolution was exactly what we needed,” explained Kimura.

A minuscule dolomite crystal

By subjecting a minuscule dolomite crystal to a solution of calcium and magnesium and pulsing the electron beam gently 4,000 times over two hours, Kimura and Yamazaki dissolved the defects.

Following these pulses, dolomite expanded by about 100 nanometers, roughly 250,000 times smaller than an inch.

This equated to approximately 300 layers of dolomite, marking a substantial leap from the previously grown maximum of five layers in a lab setting.

The insights gleaned from solving the Dolomite Problem can aid engineers in fabricating superior-quality materials for semiconductors, solar panels, batteries, and various other technologies.

In the past, crystal growers attempting to produce defect-free materials aimed for slow growth. Sun concluded that periodically dissolving defects during growth allows for the rapid growth of defect-free materials.

The study received financial support from the American Chemical Society PRF New Doctoral Investigator grant, the U.S. Department of Energy, and the Japanese Society for the Promotion of Science.

Read the original article on sciencedaily.

Read more: Unlocking Uranium from Oceans: How Rare-Earth Metal Could Simplify and Economize Extraction.