First of all, you should realize that the surface energy of solids is a function of anisotropy, especially in case of such crystalline materials like orthoferrites. Secondly, YFeO3 exists in two states (hexagonal and orthrombic) whose XRD profiles have different shapes. By this means, their surface energies even will be different for sure, so long as we consider their average values.

Michael, thank you! In my case I'm interested in approximate value. It'll be enough to estimate the size of the YFeO3 critical nucleus. 

mr Michael thanks for answer.