Table 3. Mulliken spin densities on Cu and S atoms in the α and β LUMOs of the broken symmetry singlet 2-hole Cu₄S(SH) and Cu₄S₂ models (B3LYP, TZVP on Cu, S, and ligating N atoms, and SV on all remaining atoms, PCM of 4.0).

		Mulliken spin density
		μ2L	CuI	CuII	CuIII	CuIV	μ4S2–
2-Hole SH–S = 0	α LUMO	0.16	0.37	0.06	0.06	0.04	0.20
	β LUMO	0.17	0.03	0.17	0.09	0.16	0.30
2-Hole S2–S = 0	α LUMO	0.33	0.22	0.06	0.04	0.07	0.23
	β LUMO	0.37	0.05	0.06	0.05	0.14	0.27