University of Puerto Rico
Mayagüez Campus
Chemistry Department
Departmental Seminar
Celebrating the 75th. Anniversary of the ACS of Puerto Rico
by
Dr. Gustavo Lopez
Professor in the Department of Chemistry
Lehman College (LC), City University of New York (CUNY).
Friday February 17th 2023
10:30 am
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Water: Tales of Two Liquids and Two Glasses
In general, pure substances exists in one liquid state and, if crystallization is avoided, a single glass state is formed upon fast cooling. The properties of the glass that forms depend on both the cooling and compression/decompression rates. Experiments suggest that water is surprisingly different, having two different liquid states, low density liquid (LDL) and high-density liquid (HDL), and two different glassy states, low density amorphous (LDA) and high density amorphous (HDA). These finding have far reaching effects for the potential application in cryogenic technology. In this talk I we will discuss the water liquid-liquid phase transition (LLPT) scenario in which LDL and HDL are separated by a first order phase transition line that ends in a liquid-liquid critical point (LLCP) and the relationship of this line to LDA and HDA. I will also discuss the “first order-like phase transition” between LDA and HDA. Computational studies will be presented that 1) show the existence of the LLCP, 2) how nuclear quantum effects (NQE) influence its location, and 3) how response thermodynamic functions vary with NQE in the supercritical region. Two models will be presented: 1) a simple coarse grained model termed Fermi-Jagla and 2) a more realistic q-tip4p/f model. Additionally, we will discuss how NQE affects hexagonal ice and LDA. A potential application of this water polymorphism to the cryopreservation of biomolecular systems will be discussed.
Biography: Gustavo Lopez is a professor in the Department of Chemistry at Lehman College (LC), City University of New York (CUNY). He completed a bachelor’s degree in chemistry at the University of Puerto Rico, at Humacao, and earned his PhD degree in Chemistry from the University of Massachusetts, at Amherst. Gustavo spent one year at the University of Rhode Island as a postdoctoral fellow before joining the Department of Chemistry, at Mayaguez. In 2010 he moved to LC and became a faculty member of the Chemistry and Biochemistry programs in the CUNY Graduate Center. His research centers around the development and implementation of computational methods to study systems in condensed phase. Current projects include supercooled and glassy water, cryopreservation of biomolecules, description of quantum liquids and glasses using the potential energy landscape formalism, and nano-confined liquid
