Title: Unexpected compounds in the interior of giant planets predicted from first-principles calculations

Speaker: Jian Sun (Nanjing University)

Time&Location: 12:00 pm, Feb. 21,  Room B501, Tangzhongying Building 

Abstract: The interior of planets, with high pressure and high temperature conditions, is a natural laboratory to “synthesize” many unexpected compounds, which are the basis to understand the structure and evolution of planets. In this talk, I will introduce some of our recent progress usingcrystal structure prediction [1] combined with first-principles calculations, for instance, the predictions ofnewpossible compounds (helium-water, helium-ammonia, helium-methane, helium-silica, silica-water, etc) in the interior of giant planets or exoplanets, and their exotic new states under planetary high-pressure and high-temperature conditions (superionic state, plastic state, and their coexistence) [2-6]. These new compounds and their states may have some important implications for giant planets, including demixing, magnetic field, erosion of the rocky core, etc.

Biography: Jian Sun is a professor at the Physics School and National Laboratory of Solid State Microstructures at Nanjing University. He got his B.S. and Ph.D. from Nanjing University in 2002 and 2007, respectively. After that, he spent 6 years and worked as a research fellow at NRC (Canada), Ruhr University Bochum (Germany), and the University of Cambridge (UK). In 2013, he was recruited as a professor at Nanjing University. The research interests of Professor Sun mainly focus on the machine learning and graph theory assisted crystal structure prediction method (MAGUS code), new materials design, matters in the interior of planets and their exotic states (superionic and plastic states). He has published more than 100 peer-reviewed papers in scientific journals. Professor Sun has received many prestigious honors, including the distinguished young scholar of NSFC (2021), the Van Valkenburg award (2014), the Humboldt fellowship, the Marie Curie fellowship, etc. Professor Sun is a committee member of the high pressure Physics branch of the Chinese Physics Society, the Computational Materials Science branch of the Chinese Materials Research Society, and the high pressure Chemistry branch of the Chinese Chemistry Society.

Reference:

1. Kang Xia et al., “A novel superhard tungsten nitride predicted by machine-learning accelerated crystal structure search”, Sci. Bull. 63, 817 (2018).

2. Cong Liu et al., “Multiple superionic states in helium-water compounds”, Nature Physics 15, 1065 (2019).

3. Cong Liu et al., “Plastic and Superionic Helium Ammonia Compounds under High Pressure and High Temperature”, Phys. Rev. X 10, 021007 (2020).

4. Cong Liu et al., “Mixed coordination silica at megabar pressure”, Phys. Rev. Lett. 126, 035701 (2021).

5. Hao Gaoet al., “Superionic Silica-Water and Silica-Hydrogen Compounds in the Deep Interiors of Uranus and Neptune”, Phys. Rev. Lett. 128, 035702 (2022).

6. Shuning Pan et al., “Magnesium Oxide-Water Compounds at Megabar Pressure and Implications on Planetary Interiors”, (submitted)