Table 3.

QM, MM, and QM∕MM results for the structure and binding energy of the water dimer.

Model	Basis set	dH-bond (Å)	dOO (Å)	∠α	∠β
Experimenta	⋯	⋯	2.976	6±20°	57±10°
Fully QM results
GAUSSIAN[MP4]	6-311+G(d,p)	1.981	2.942	0.6°	58.1°
GAUSSIAN[B3LYP]	6-311+G(d,p)	1.933	2.900	3.5°	54.1°
GAUSSIAN[BLYP]	6-311+G(d,p)	1.950	2.927	3.8°	57.0°
GAUSSIAN[LDA]	6-311+G(d,p)	1.727	2.707	5.6°	61.7°
CPMD[BLYP]b	Plane wave	1.982	2.961	0.9°	54.1°
CPMD[LDA]c	Plane wave	1.752	2.742	0.6°	57.0°
Hybrid QM∕MM results
CPMD[BLYP]∕GROMACSd	pw∕[s3p]	1.989	2.962	6.8°	58.8°
CPMD[BLYP]∕GROMACSe	pw∕[s]	1.982	2.963	0.3°	69.7°
CPMD[LDA]∕GROMACSf	pw∕[s3p]	1.986	2.952	5.5°	60.7°
CPMD[LDA]∕GROMACSg	pw∕[s]	1.971	2.950	2.3°	67.4°

^aReference ²⁵.

^bCPMD results using Martin–Truhler pseudopotential with BLYP functional.

^cCPMD results using Godecker pseudopotential with LDA functional.

^dQM∕MM results using Martin–Truhler pseudopotential with BLYP functional for CPMD and partial wave expansion ℓ_max=1;(s,p₁,p₀,p₋₁) for MM atoms.

^eQM∕MM results using Martin–Truhler pseudopotential with BLYP functional for CPMD and partial wave expansion ℓ_max=0;(s) for MM atoms.

^fSame as in Footnote d but using Godecker pseudopotential with LDA functional.

^gSame as in Footnote e but using Godecker pseudopotential with LDA functional.