Water octupole moments

Overall, the QM results indicate both a large quadrupole and out-of-plane character in the charge distribution of a water molecule in the liquid phase. Only SSDQOl has multipoles consistent with both features, although somewhat too little for the former and too much for the latter. Furthermore, it was shown that multisite models require at least six points to reproduce moments consistent with the QM results [55], as has also been found for polarizable multisite models [37, 57]. On the other hand, it was also shown [55] that multipole models are able to reproduce electrostatic potentials due to the QM charge distribution with moments up to the octupole. 

Ichiye, T, and Tan, M. L. [2006). Soft sticky dipole-quadrupole-octupole potential energy function for liquid water An approximate moment expansion,/ Chem. Phys., 124, pp. 134504. 

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