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Speaker Photo
lei-xu.jpg
Speaker University
The Chinese University of Hong Kong, China
Speaker Biography

8/2018-present - Professor, Physics Department, The Chinese University of Hong Kong
8/2015-8/2018 - Associate Professor, Physics Department, The Chinese University of Hong Kong
8/2009-8/2015 - Assistant Professor, Physics Department, The Chinese University of Hong Kong
2006-2009 - Harvard University, School of Engineering and Applied Sciences, Post-doc Fellow
2000-2006 - The University of Chicago, Department of Physics, Ph.D.
1995-2000 - The University of Science and Technology of China, Department of Physics, B.S.

Question
Revealing the three-component structure of water with principal component analysis (PCA) of X-ray spectra
Answer

Combining principal component analysis (PCA) of X-ray spectra with MD simulations, we experimentally reveal the existence of three basic components in water. These components exhibit distinct structures, densities, and temperature dependencies. Among the three, the two major components correspond to the low-density liquid (LDL) and the high-density liquid (HDL) predicted by the two-component model, and the third component exhibits a unique 5-hydrogen-bond configuration with ultra-high local density. As the temperature increases, the LDL component decreases and the HDL component increases, while the third component varies non-monotonically with a peak around 20 °C to 30 °C. The 3D structure of the third component is further illustrated as the uniform distribution of five hydrogen-bonded neighbors on a spherical surface. Our study reveals experimental evidence for water's possible three-component structure, which provides a fundamental basis for understanding water's special properties and anomalies.

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