Table 1. Calculated lattice parameters (a, b, and c in Å), volume (V₀ in ų/atom), relative energies with respect to that of black phosphorus (ΔE in eV/atom), and energy band gaps (E_g in eV).

	a	b	c	V0	ΔE	Eg
K4	5.37a	5.37	5.37	19.36a	0.02a	1.13a
	5.32b	5.32	5.32	18.82a	0.04b	1.54d (1.07b)
A17	3.28a	11.22a	4.54a	20.89a	—	—
	3.32b	10.43b	4.41b	19.09a	—	0.36d (0.08a)
	3.3133c	10.473c	4.374c	18.97a	—	0.335c

^aOur calculated results at the PBE level.

^bOur calculated results at the GGA-D2 level.

^cExperimental data¹².

^dOur calculated results at the HES06 level.