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By simulating the vibrational spectra of water clusters of increasing size using quantum-derived semiclassical spectroscopy, Ceotto and his team looked to see when the spectra matched that of bulk water. ‘With just a few water molecules, which make up to two solvation shells, the physics of vibration in liquid water is recovered,’ explains Ceotto. In a simple description of water, individual molecules can be thought of as being a double donor and double acceptor of hydrogen bonds. And although Ceotto’s team’s findings show that tetrahedral coordination is necessary, they suggest it is insufficient on its own to be reflective of bulk water.