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Proposing Institution

Theoretical Chemistry, Ruhr-University Bochum
Project Manager

Philipp Schienbein
Universitätsstr. 150
44801 Bochum
Supercritical water (SCW) is characterized by state parameters above the critical point (T = 647 K, P = 22.1 MPa, d = 0.32 g/cm3). The study of such supercritical liquids is not merely an academic issue, but is also motivated by their importance in technological and industrial processes. SCW in particular has already found use in the treatment of hazardous wastes, in noncatalytic chemical reactions, and in nanosynthesis. The potential applications are made possible by the peculiar characteristics of SCW. Water so far from ambient conditions possesses very different physical properties than at 300 K and 1 atm. The macroscopic changes seem to be driven at the microscopic level mainly by significant alterations in the hydrogen-bonded network of water at extreme conditions. Vibrational spectroscopy remains one of the most important techniques in the studies of water, being sensitive to cluster size, H-bond abundance and average H-bond energy. (Terahertz) THz spectroscopy, in particular, has been shown to be the most powerful technique since it probes directly the picosecond range where H-bond fluctuations take place. In this project, we intend to perform extensive ab initio molecular dynamics (AIMD) simulations of carefully selected state points in the supercritical and possibly near-critical regime of water. The analysis methodology formulated and further developed in our research group allows us to obtain a spatially-resolved picture of the IR absorption cross section down to the THz regime. In this way, correlated molecular dipole fluctuations that contribute significantly to the IR response of liquid water can be decomposed in terms of distinct solvation shells. In this project we will address how the hydrogen-bonded structure seen at a molecular level affects the THz~spectra of SCW, where the enhanced fluctuations near the critical point will create percolating clusters and thus interfaces that promise rich low-frequency spectra.

Impressum, Conny Wendler