Table 2. Binding Energies Calculated (in kcal/mol) at the MP2/aug-cc-pVTZ(PP) and CCSD(T)/CBS Levels of Theory for the (X-T-X₃)₂ Homodimers (Where T = C, Si, and Ge, and X = F, Cl, and Br) at the Most Favorable T/X···T/X Distances (in Å).

homodimer	distancea (Å)	EMP2/aug – cc–pVTZb (kcal/mol)	ECCSD(T)/CBS (kcal/mol)	distancea (Å)	EMP2/aug – cc–pVTZb (kcal/mol)	ECCSD(T)/CBS (kcal/mol)
	tetrel···tetrel			tetrel···halogen
(F-C-F3)2	4.03	–0.60	–0.74	3.37	–0.49	–0.60
(Cl-C-Cl3)2	4.69	–2.99	–2.53	3.91	–2.00	–1.75
(Br-C-Br3)2	4.95	–3.96	–3.52	4.05	–2.98	–2.67
(F-Si-F3)2	4.78	–0.05	–0.14	3.25	–1.01	–1.26
(Cl-Si-Cl3)2	4.79	–3.17	–2.77	4.00	–1.70	–1.49
(Br-Si-Br3)2	4.98	–4.42	–3.98	4.14	–2.51	–2.25
(F-Ge-F3)2	noc	noc	noc	3.17	–1.34	–1.68
(Cl-Ge-Cl3)2	4.79	–3.27	–2.92	3.98	–1.79	–1.57
(Br-Ge-Br3)2	5.00	–4.57	–4.13	4.11	–2.63	–2.37
	type III halogen···halogen			type II halogen···halogen
(F-C-F3)2	2.96	–0.27	–0.32	3.09	–0.52	–0.64
(Cl-C-Cl3)2	3.44	–0.74	–0.68	3.45	–2.19	–1.95
(Br-C-Br3)2	3.54	–1.01	–0.92	3.49	–3.41	–3.06
(F-Si-F3)2	3.25	–0.08	–0.14	3.01	–0.87	–1.06
(Cl-Si-Cl3)2	3.56	–0.80	–0.77	3.56	–1.78	–1.61
(Br-Si-Br3)2	3.66	–1.12	–1.05	3.66	–2.60	–2.34
(F-Ge-F3)2	3.18	–0.10	–0.16	2.95	–1.06	–1.31
(Cl-Ge-Cl3)2	3.50	–0.90	–0.86	3.51	–1.91	–1.75
(Br-Ge-Br3)2	3.60	–1.26	–1.18	3.61	–2.79	–2.55

^aThe most favorable T/X···T/X distances were determined according to the corresponding PES curves (see Figure 4).

^bPP functions were implemented for Ge and Br atoms.

^cNo local energy minimum was observed in the corresponding PES curve (see Figure 4).