Extended Data Figure 10: Comparison of the ratio of the lattice parameters c/a for hcp Os.
From: The most incompressible metal osmium at static pressures above 750 gigapascals
The ratio is calculated using the RSPt method at T = 0 K with a PBE-GGA (red dashed line), and using Wien2k with a LDA (green line) and a PBE-GGA (blue line). The room-temperature experimental results obtained in this work are shown with filled black dots. Agreement between the calculated and experimental c/a ratio is typical for DFT calculations. The theoretical results do not show any peculiarity of the lattice-parameter ratio; however, the calculations are carried out at T = 0 K, whereas the experimental data are taken at room temperature. Therefore, a direct comparison between theory and experiment is nontrivial (Methods). In hcp metals, the effect of the electronic transitions on the lattice-parameter ratio should become visible at finite temperatures, owing to the peculiarities of the thermal expansion coefficients, which are anisotropic along different directions of the crystal lattice.
