q-TIP4P/F model of water

The q-TIP4P/F model is a flexible version of the TIP4P/2005 model of water designed for use in path integral simulations.

Melting point

The melting point was found to be $251\pm 1.5K$ at 1 bar via direct coexistence calculations, and at 257K from calculations of the Gibbs energy function .

Isotope effects

Melting point (extract from the Ice Ih page)

$T_m$ (D20)	Pressure	Water model/technique	Reference
$257.5(5)K$	1 bar	q-TIP4P/F
$276.83\pm 0.02K$	1 bar	experimental value

$T_m$ (T20)	Pressure	Water model/technique	Reference
$259.2(5)K$	1 bar	q-TIP4P/F
$277.64K$	0.6629 kPa	experimental value

It is worth pointing out that the calculations presented in the work of Ramírez and Herrero used the melting point of the q-TIP4P/F model as its "reference state". It is perhaps more fruitful to examine the relative changes upon isotopic substitution: $\mathrm{\Delta }{T}_m(D_{2}O-H_{2}0)=6.5K$ (experimental value: 3.68 K) and $\mathrm{\Delta }{T}_m(T_{2}O-H_{2}0)=8.2K$ (experimental value: 4.49 K).

Ice Ih

Isotope effects have also been studied for ice Ih .