Comment on “High-Pressure Behavior of Hydrogen and Deuterium at Low Temperatures”

X.-D. Liu et al. [Phys. Rev. Lett. 119, 065301 (2017)] report on the existence of a new unique solid phase of ${\mathrm{D}}_2$, which makes the high-pressure low-temperature behavior distinct from ${\mathrm{H}}_2$. Here, based on the analysis of their Raman data and phase transition theory, we show that the presented data do not support this claim.

Figure 1

Observations of the dips in the temperature dependent vibron Raman spectra of ${\mathrm{D}}_2$ at 132 GPa [5]. Red curve is a manual fit to the data using the Mayer-Saupe order parameter [3].