Table 2.

CPU time (hour) needed to run 100 ps molecular dynamics simulations (1 fs integration time step) for cubic boxes of water, consisting of 216 and 1728 water molecules, using the spherical cutoff scheme for column 2 and the X-Pol-Ewald method for electrostatics beyond the nearest neighbor in columns 2 and 3. A real-space Ewald cutoff distance of 9 angstroms was used in all simulations for comparison. The column under Full lists the time using the full update of Ewald long-range electrostatic correction to the Fock matrix at every SCF iteration (eqn (21)), and MIC denotes calculations using the mean-field image-potential correction approximation (eqn (23)). All calculations were performed using the AM1 method and full computation. All calculations were performed using the AM1 method and full computation details can be found in the text

system	X-Pol cutoff	X-Pol-Ewald
		Full	MIC
216	6.4	8.1	7.0
1728	58.5	73.3	65.0