Extended Data Fig. 7: Energy of the PdH slab growth.
From: Metastable hexagonal close-packed palladium hydride in liquid cell TEM
a, b, Energy required to symmetrically add Pd (a) or H (b) atomic layers on top of the (0001) hcp PdH or (111) fcc PdH slab, estimated from DFT calculations. c, Illustration of the symmetric addition of Pd and H layers, with Pd and H atoms drawn in gray and blue, respectively. The energies are defined as ΔEPd(N) = 1/2×((E(PdNHN−1)−E(PdN−2HN−1)−2×E(fcc Pd)) for the addition of N Pd atoms in a and ΔEH(N) = 1/2×((E(PdNHN+1)−E(PdNHN−1)−E(H2)) for the addition of N H atoms in b. In the case of fcc and hcp Pd slabs, the energy for Pd addition is simply expressed as ΔEPd(N) = E(PdN)−E(PdN−1)−E(fcc Pd); for fcc Pd, ΔEPd(N) approaches zero, whereas for hcp Pd, it approaches the energy difference between bulk hcp Pd and fcc Pd, which indicates that convergence has been achieved. Although ΔEPd(N) for hcp PdH and hcp Pd are similar, ΔEPd(N) for fcc PdH is higher than that for fcc Pd and even than that for hcp PdH.
