Fig. 4. Crystal structure of the (PH₃)₂H₂ vdW compound.

Crystal structure of the (PH₃)₂H₂ vdW compound at 5.5 GPa and room T (a) with views along the c (b), a (c), and b (d) crystal axes. The orange spheres represent the PH₃ molecules, whereas the white spheres represent the H₂ molecules. The size of the spheres has been drawn by estimating their radius as the sum of the P–H bond length (1.421 Å)² and H van der Waals radius (1.20 Å)⁴⁹ in the case of PH₃ (2.62 Å) and as the sum of the H van der Waals radius (1.20 Å)⁴⁹ and half of the H–H distance (0.742 Å)⁷⁴ in the case of H₂ (1.571 Å).