Water is a major component of fluids in the Earth's mantle, where its properties are substantially different from those at ambient conditions. At the pressures and temperatures of the mantle, experiments on aqueous fluids are challenging, and several fundamental properties of water are poorly known; e.g., its dielectric constant has not been measured. This lack of knowledge of water dielectric properties has greatly limited our ability to model water-rock interactions and, in general, our understanding of aqueous fluids below the Earth's crust. Using ab initio molecular dynamics, we computed the dielectric constant of water under the conditions of the Earth's upper mantle, and we predicted the solubility products of carbonate minerals [1]. We found that MgCO3 (magnesite)---insoluble in water under ambient conditions---becomes at least slightly soluble at the bottom of the upper mantle, suggesting that water may transport significant quantities of oxidized carbon. We also computed the electronic dielectric constant of water as a function of pressure and we found that, contrary to expectations based on widely used simple models, both the refractive index and the electronic band gap of water increase under pressure [2].
[1] D. Pan, L. Spanu, B. Harrison, D. A. Sverjensky and G. Galli, PNAS 110, 6646 (2013);
[2] D. Pan, Q. Wan, G. Galli, Nat. Commun. 5, 3919 (2014).
Ding Pan is a postdoctoral scholar in the Institute for Molecular Engineering at the University of Chicago, and a scientist in the deep carbon observatory supported by the Alfred P. Sloan Foundation. He obtained B.S. in Physics in the 00 Class at University of Science and Technology of China in 2005, and Ph.D. at Institute of Physics, CAS in 2010. During the PhD study, he was a visiting researcher at the Fritz-Haber-Institute of the Max Planck Society in Berlin, Germany and a Thomas Young Centre Junior Research Fellow at the University College London, UK. From 2011 to 2014, he was a research associate in UC Davis.
His research interests lie in studying the novel structural and electronic properties of complex materials, by developing and applying multi-scale modeling methods, such as first-principles and force-field-based simulations. The properties of ice surfaces and the interactions between water and other substances in a very broad pressure (P) and temperature (T) range are his research emphasis. He has published more than ten papers in high profile journals, such as Nature Materials, Nature communications, PNAS and PRL, and was invited to give talks at some of the most influential conferences including APS March meeting, MRS Spring meeting and CPMD meeting.