J. Hooper, Tyson Terpstra, Andrew Shamp
Mar 18, 2014
Citations
0
Influential Citations
51
Citations
Journal
Journal of Physical Chemistry C
Abstract
The structures of the strontium polyhydrides, SrHn with n > 2, under pressure are studied using evolutionary algorithms coupled with density functional theory calculations. A number of phases with even n are found to be thermodynamically stable below 150 GPa. Particularly interesting is the SrH4 stoichiometry, which comprises the convex hull at 50, 100, and 150 GPa. Its hydrogenic sublattice contains H2 and H– units, and throughout the pressure range considered, it adopts one of two configurations which were previously predicted for CaH4 under pressure. At 150 GPa, the SrH6 stoichiometry has the lowest enthalpy of formation. The most stable configuration assumes P3 symmetry, and its lattice consists of one-dimensional H2···H– hydrogenic chains. Symmetrization of these chains results in the formation of ∞1[Hδ−] helices, which are reminiscent of the trigonal phase of sulfur. The R3m-SrH6 phase, which is comprised of these helices, becomes dynamically stable by 250 GPa and has a high density of states at t...