Table 4.

Summary of mDC and DFTB2 cluster binding energy (ΔE) and cluster relative energies (ΔΔE) errors (kcal mol⁻¹) relative to the MP2, MP2+CP, and 〈MP2〉 reference values. The coordinate root mean square statistics (a.u.) are relative to the structure before geometry optimization, which are the DFTB2 isolated waters superimposed onto the optimized MP2 cluster geometry.

Ref.	Cluster		ΔE		ΔΔE		rms
			mDC	DFTB2	mDC	DFTB2	mDC	DFTB2
MP2	(H2O)4	mse	3.38	11.57	−1.65	−2.90	···	···
		mue	3.38	11.57	1.69	2.90	0.28	0.66
		max	4.78	13.89	−4.08	−5.15	0.48	2.03
	(H2O)5	mse	5.73	16.86	−0.78	−2.38	···	···
		mue	5.73	16.86	0.80	2.38	0.37	0.61
		max	6.47	18.90	−2.69	−4.73	1.08	1.23
	(H2O)6	mse	7.57	21.88	−0.08	−0.74	···	···
		mue	7.57	21.88	0.36	1.15	0.40	0.73
		max	8.26	23.78	−0.81	−7.24	1.35	2.88
MP2+CP	(H2O)4	mse	−2.91	5.28	−0.49	−1.74	···	···
		mue	2.91	5.28	0.69	1.74	···	···
		max	−4.87	6.67	−2.35	−3.42	···	···
	(H2O)5	mse	−3.34	7.79	0.11	−1.49	···	···
		mue	3.34	7.79	0.54	1.49	···	···
		max	−4.72	9.07	−1.28	−3.32	···	···
	(H2O)6	mse	−4.09	10.22	0.55	−0.11	···	···
		mue	4.09	10.22	0.55	0.92	···	···
		max	−4.61	11.78	1.65	−4.86	···	···
〈MP2〉	(H2O)4	mse	0.23	8.42	−1.07	−2.32	···	···
		mue	1.09	8.42	1.13	2.32	···	···
		max	−2.13	10.28	−3.22	−4.28	···	···
	(H2O)5	mse	1.19	12.33	−0.33	−1.93	···	···
		mue	1.34	12.33	0.52	1.93	···	···
		max	1.90	13.99	−1.98	−4.02	···	···
	(H2O)6	mse	1.74	16.05	0.24	−0.43	···	···
		mue	1.74	16.05	0.33	1.01	···	···
		max	2.54	17.78	1.02	−6.05	···	···