Water is perhaps the most ubiquitous, and the most essential, of any molecule on earth. Indeed, it defies the imagination of even the most creative science fiction writer to picture what life would be like without water. Despite decades of research, however, water's puzzling properties are not...

We study a three-dimensional system of particles interacting via spherically symmetric pair potentials consisting of several discontinuous steps. We show that at certain values of the parameters describing the potential, the system has three first-order phase transitions between fluids of...