These considerations suggest that similar principles used to parameterize other three-site rigid water models generally encounter similar limitations (i.e., the challenges and constraints faced in developing and optimizing water models based on similar principles are likely to be shared). To reduce the uncertainty in the model outcomes, another possible solution is to employ extra sites in the model, such as in the four-site models like TIP4P 17 or TIP4P-ICE. Such an addition permits to expand the degrees of freedom to tune, allowing for a better fit of some properties , e.g., the curve of density across different temperatures.