title: Dynamical stability of Fe-H in the Earth's mantle and core regions.
abstract: The core extends from the depth of 2,900 km to the center of the Earth and is composed mainly of an iron-rich alloy with nickel, with 10% of the mass comprised of lighter elements like hydrogen, but the exact composition is uncertain. We present a quantum mechanical first-principles study of the dynamical stability of FeH phases and their phonon densities of states at high pressure. Our free-energy calculations reveal a phonon-driven stabilization of dhcp FeH at low pressures, thus resolving the present contradiction between experimental observations and theoretical predictions. Calculations reveal a complex phase diagram for FeH under pressure with a dhcp --> hcp --> fcc sequence of structural transitions.
authors.affiliation: Theoretical Physics Department, Moscow State Institute of Steel and Alloys (Technological University), 4 Leninskii Prospect, Moscow 119049, Russia.
authors.forename: Eyvaz I
authors.initials: EI
authors.lastname: Isaev
authors.forename: Natalia V
authors.initials: NV
authors.lastname: Skorodumova
authors.forename: Rajeev
authors.initials: R
authors.lastname: Ahuja
authors.forename: Yuri K
authors.initials: YK
authors.lastname: Vekilov
authors.forename: Börje
authors.initials: B
authors.lastname: Johansson