Ji et al. report performing X-ray diffraction on hydrogen compressed to over 250 GPa (https://doi.org/10.1038/s41586-019-1565-9). It is a remarkable technical achievement. However, the experimental data presented and discussed in the paper do not support the main conclusion that hydrogen undergoes an isostructural phase transition and preserves the hexagonal close packed (hcp) structure up to the highest pressure achieved. The behavior of compressed hydrogen in the studied pressure range cannot be explained by electronic topological transition (ETT), as claimed in the paper.
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