Fig. 5: The missing tile of P for group 15.

Non-metal region of the Periodic Table showing the elements (yellow and orange) able to form crystalline X2H2 vdW compounds (X = CH419, PH3, H2S26, H2Se27, HI57) having the I4cm (I4/mcm) structure, with P (X = PH3), highlighted in orange, representing the so far missing tile for group 15 elements reported in this study (see text).