Phase Diagram of Water Revised by Sandia Researchers
Supercomputer simulations by two Sandia researchers have significantly altered the theoretical diagram universally used by scientists to understand the characteristics of
water at extreme temperatures and pressures. The new computational model also expands the known range of water’s electrical conductivity. The Sandia theoretical work showed that phase boundaries for “metallic water” — water with its electrons able to migrate like a metal’s — should be lowered from 7,000 to 4,000 kelvin and from 250 to 100 gigapascals. (A phase boundary describes conditions at which materials change state — think water changing to steam or ice, or in the present instance, water — in its pure state an electrical insulator — becoming a conductor.) The lowered boundary is sure to revise astronomers’ calculations of the strength of the magnetic cores of gas-giant planets like Neptune. Because the planet’s temperatures and pressures lie partly in the revised sector, its electrically conducting water probably contributes to its magnetic field, formerly thought to be generated only by the planet’s core. The calculations agree with experimental measurements in research led by Peter Celliers of Lawrence Livermore National Laboratory. Sandia is a National Nuclear Security Administration laboratory.