mW model of water

The mW model of water is an atom with tetrahedrality intermediate between carbon and silicon. mW mimics the hydrogen-bonded structure of water through the introduction of a nonbond angular dependent term that encourages tetrahedral configurations. The model is given by:

$E=\sum _{i}\sum _{j>i}\Phi _{ij}(r_{ij})+\sum _{i}\sum _{j\neq i}\sum _{k>j}\Phi _{ijk}(r_{ij},r_{ik},\theta _{ijk})$

where

$\Phi _{ij}(r_{ij})=A\epsilon \left[B\left({\frac {\sigma }{r}}\right)^{p}-\left({\frac {\sigma }{r}}\right)^{q}\right]\exp \left({\frac {\sigma }{r-a\sigma }}\right)$

and

$\Phi _{ijk}(r_{ij},s_{ik},\theta _{ijk})=\lambda \epsilon \left[\cos \theta -\cos \theta _{0}\right]^{2}\exp \left({\frac {\gamma \sigma }{r-a\sigma }}\right)\exp \left({\frac {\gamma \sigma }{s-a\sigma }}\right)$

where

$A=7.049556277$, $B=0.6022245584$, $p=4$, $q=0$, and $\gamma =1.2$

References

Related reading

• Emily B. Moore and Valeria Molinero "Ice crystallization in water’s “no-man’s land”", Journal of Chemical Physics 132, 244504 (2010)