Simulation of dolomite growth near ambient conditions

For 200 years, scientists have failed to grow a common mineral in the laboratory under the conditions believed to have formed it naturally. Now, a team of researchers from the University of Michigan and Hokkaido University in Sapporo, Japan have finally pulled it off, thanks to a new theory developed from atomic simulations. The secret to finally growing dolomite in the lab was removing defects in the mineral structure as it grows, as demonstrated by this simulation run at 10 times the original speed. Magnesium (orange squares) attach to a growing dolomite surface in water, which consists of alternating rows of magnesium and calcium (white squares). The calcium and magnesium levels in the water fluctuate throughout the simulation (shown in graph in top left panel). When the levels are high (or “supersaturated“), calcium and magnesium randomly attach to a layer of the crystal (the square panel on the right), often lodging into the wrong spot and creating defects (orange squares with blue borders). The defects prevent additional layers of dolomite from forming, which slows dolomite growth to a crawl. Ten million years are required to make just one layer of ordered dolomite. Luckily these defects aren’t locked in place. When the calcium and magnesium levels are low (or “undersaturated“), they detach as the crystal dissolves (gray squares). Because the disordered atoms are less stable than atoms in the correct position, they are the first to dissolve when the mineral is washed with water. Repeatedly rinsing away these defects—for example with rain or tidal cycles—allows a dolomite layer to form in only a matter of years. Over geologic time, mountains of dolomite can accumulate. The panels on the left show the following, in descending order: the saturation state of calcium and magnesium in the surrounding water, the amount of calcium relative to the total of both calcium and magnesium, and the relative number of correctly ordered calcium and magnesium atoms, and the amount of energy created with the formed structure. Gray areas depict vacancies in the dolomite later, white spaces depict calcium and carbonate. The red dot in the graphs on the left shows the current state of the simulation. This research is published in the paper: “Dissolution enables dolomite crystal growth near ambient conditions.“ Read more: Wenhao Sun, the corresponding author, is the Dow Early Career Professor of Engineering and an assistant professor of materials science and engineering. Learn more about the Sun Research Group: