Sources of the deficiencies in the popular SPC/E and TIP3P models of water

Abstract

Motivated by the results of Vega et al. [J. Phys. Condens. Matter 20, 153101 (2008)] about the phase diagram of water, and by the results of Kiss and Baranyai [J. Chem. Phys. 131, 204310 (2009)] about the properties of gas-phase clusters, we carried out a comparative study of the structure modeled by SPC∕E and TIP3P interactions in ambient liquid water. The gas-phase clusters of SPC∕E and TIP3P models show erroneous structures, while TIP4P-type models, either polarizable or not, provide qualitatively correct results. The trimers of SPC∕E and TIP3P are planar in gas phase, contrary to experimental and TIP4P-type models. The aim of this study was to see whether traces of these false geometries characteristic to SPC∕E and TIP3P in gas phase can also be found in the liquid phase. For this purpose we selected trimers formed by adjacent neighbors of water molecules in the liquid and calculated their geometrical features. We determined angles formed by the HO bonds of the molecules with OO vectors and with the normal vector of the OOO plane in the selected trimers. Our results showed that, despite high temperature, the SPC∕E and TIP3P water contains larger number of planar arrangements than other TIP4P-type models. Although structural differences presented in this study are small, they are accurately detectable. These results weaken the reliability of studies obtained by the SPC∕E or TIP3P models even in the liquid phase.