Table 2. Interaction Energies (kcal/mol) and Error Statistics (in Percent) for Selected Systems of the A24 Data Set^a.

					CAS		CASc
	HF	CAS	HF + DISP	HFc + DISP	+DISP	+DispCAS	+DISP	+DispCAS	ref.
H2O–H2O	–3.628	–2.710	–6.078	–4.859	–5.045	–5.012	–4.752	–4.719	–5.006
HCN–HCN	–4.100	–3.408	–5.866	–4.850	–5.108	–5.084	–4.695	–4.671	–4.745
HF–HF	–3.742	–2.741	–5.635	–4.294	–4.526	–4.505	–4.109	–4.088	–4.581
HF–CH4	–0.257	0.168	–1.839	–1.725	–1.347	–1.328	–1.628	–1.609	–1.654
HCOH–HCOH	–2.458	–0.656	–6.659	–4.743	–4.749	–4.718	–4.410	–4.379	–4.554
C2H2–C2H2(1)	–0.511	–0.254	–1.922	–1.724	–1.637	–1.637	–1.577	–1.577	–1.524
C2H4–C2H4(1)	0.902	0.801	–1.232	–1.280	–1.299	–1.281	–1.204	–1.186	–1.090
Ar–CH4	0.355	0.350	–0.494	–0.456	–0.470	–0.470	–0.425	–0.425	–0.405
Ar–C2H4	0.430	0.356	–0.348	–0.415	–0.409	–0.409	–0.390	–0.390	–0.364
C2H4–C2H2b	3.400	2.643	1.116	0.540	0.368	0.412	0.557	0.601	0.821
C2H4–C2H4(2)b	3.877	2.975	1.304	0.598	0.403	0.447	0.624	0.667	0.934
C2H2–C2H2(2)b	3.476	2.752	1.448	0.924	0.738	0.784	0.928	0.974	1.115
Δ̅	140	128	–6.4	–12.2	–16.2	–14.6	–7.3	–5.7
Δ̅abs	141	128	24.7	13.7	19.4	18.1	10.8	9.7
σ	112	71.5	27.7	13.1	22.5	20.8	13.9	12.2
Δmax	315	222	46.2	35.9	56.8	52.2	33.2	28.5

^aHFc and CASc denote supermolecular HF and CASSCF interaction energies, respectively, corrected for the first-order SAPT(PBE0AC) energy. “CAS plus dispersion” models include the dispersion energy obtained at the SAPT(PBE0AC) level of theory in the aug-cc-pVTZ + (3322) basis. For the “CAS + DispCAS” and “CASc + DispCAS” methods, see eqs 58 and 59, respectively. “Ref.” is the CCSD(T)/CBS benchmark of ref (70).

^bNonequilibrium geometry.