No / By extending the cleaving method to molecular systems, we perform direct calculations of the ice Ih-water interfacial free energy for the TIP4P model. The values for the basal, prism, and f11 20g faces are 23:3 0:8 mJm 2, 23:6 1:0 mJm 2, and 24:7 0:8 mJm 2, respectively. The closeness of these values implies a minimal role of thermodynamic factors in the anisotropic growth of ice crystals. These results are about 20% lower than the best experimental estimates. However, the Turnbull coefficient is about 50% higher than for real water, indicating a possible limitation of the TIP4P model in describing freezing. / EPSRC