  Despite the importance of ice nucleation, this process has been barely
explored at negative pressures. Here, we study homogeneous ice nucleation in
stretched water by means of Molecular Dynamics Seeding simulations using the
TIP4P/Ice model. We observe that the critical nucleus size, interfacial free
energy, free energy barrier, and nucleation rate barely change between isobars
from -2600 to 500 bar when they are represented as a function of supercooling.
This allows us to identify universal empirical expressions for homogeneous ice
nucleation in the pressure range from -2600 to 500 bar. We show that this
universal behavior arises from the pressure dependence of the interfacial free
energy which we compute by means of the mold integration technique finding a
shallow minimum around -2000 bar. Likewise, we show that the change in the
interfacial free energy with pressure is proportional to the excess entropy and
the slope of the melting line, exhibiting the latter a reentrant behavior also
at the same negative pressure. Finally, we estimate the excess energy and the
excess entropy of the ice Ih-water interface.
