Contents

16 February 1996
Vol 271, Issue 5251

About The Cover

The isolated water pentamer adopts a ring structure, with each molecule acting as a single donor and single acceptor of a hydrogen bond. The average separation between oxygen atoms (red spheres) is 2.76 angstroms. Similar water pentagons are prominent structures in the dynamic hydrogen-bonding network revealed in computer simulations of liquid water, like that depicted in the background. See 929 in the Special Section on clusters beginning on 920, and a related Report (963). [Image: Tim Robinson, Chemistry Graphics Facility, University of California, Berkeley]