SPC/E model of water

The extended simple point charge model, SPC/E is a slight reparameterisation of the SPC model of water, with a modified value for $q_{\mathrm {O} }$. The molecule is modelled as a rigid isosceles triangle, having charges situated on each of the three atoms. Apart from Coulombic interactions, the molecules interact via long-range Lennard-Jones sites, situated on the oxygen atoms. The parameters are as follows:

parameter	value
$\sigma$	$3.166{\mathrm {\AA} }$
$\epsilon$	$0.650$ kJ mol-1
$r_{\mathrm {OH} }$	$1.000\mathrm {\AA}$
$\angle _{\mathrm {HOH} }$	$109.47^{\circ }$
$q_{\mathrm {O} }$	$-0.8476e$
$q_{\mathrm {H} }$	$q_{\mathrm {O} }/2$ (charge neutrality)
$r_{\mathrm {OM} }$	$0$ (charge sits on oxygen)

The SPC/E model has a dipole moment of 2.351 D. (Ref. 1 Table I),

References

1. H. J. C. Berendsen, J. R. Grigera, and T. P. Straatsma "The missing term in effective pair potentials", Journal of Physical Chemistry 91 pp. 6269 - 6271 (1987)
2. Swaroop Chatterjee, Pablo G. Debenedetti, Frank H. Stillinger, and Ruth M. Lynden-Bell "A computational investigation of thermodynamics, structure, dynamics and solvation behavior in modified water models", Journal of Chemical Physics 128 124511 (2008)