EarthRef.org Digital Archive (ERDA) -- The influence of hydrogen on the seismic properties of solid iron

Description
Based on first-principles calculations, we observe that hydrogen has a strong effect on decreasing the density of the hexagonal close-packed structure of iron. The structural effect is weakly dependent on the ordering pattern of the H defects. However, hydrogen also hardens iron at core pressures. Both the compressional and the shear wave velocities increase with addition even of small amounts of H; the increase of shear going against the geophysical requirements for light elements. This aspect makes hydrogen an undesirable light element in the Earth's core if we try to fit the seismological observations.