Earth’s core could contain helium from the early solar system. The noble gas tucks into gaps in iron crystals under high pressure and temperature.

Iron is one of the main elements found in the Earth's inner core ... "Additionally, we determined that the phase of pure iron at 240 GPa and 5,345 K, just before melting, is hexagonal close ...

It is made of only one type of atom: iron atoms. Sulfur is another element. It contains only sulfur atoms, and nothing else, so it is pure. When we mix two different pure substances together ...

At room temperature, a pure bar of neodymium wouldn’t be ... and partly to do with the electronic structure of the elements in the alloy. Iron normally has a unit cell that’s either body ...