Comparison of the volumes per Fe atom (V/Z) of Fe and Fe-H phases observed in our experiments and the volume previously reported at 300 K. Both the fcc and dhcp FeH _x phases observed in this study (red and green circles, respectively) show V/Z consistent with 1:1 stoichiometric FeH (colored curves). Equations of state for hcp Fe, fcc FeH, dhcp FeH, and FeH₂ are from Dewaele et al. (2006), Narygina et al. (2011), Pepin et al. (2014), and Pepin et al. (2014), respectively.