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We propose a sharp interface model for simulating solid-state dewetting wherethe surface energy is (weakly) anisotropic. The morphology evolution of thinfilms is governed by surface diffusion and contact line migration. Themathematical model is based on an energy variational approach. Anisotropicsurface energies lead to multiple solutions of the contact angle equation atcontact points. Introduction of a finite contact point mobility is bothphysically based and leads to robust, unambiguous determination of the contactangles. We implement the mathematical model in an explicit finite differencescheme with cubic spline interpolation for evolving marker points. Followingvalidation of the mathematical and numerical approaches, we simulate theevolution of thin film islands, semi-infinite films, and films with holes as afunction of film dimensions, Young's angle $\theta_i$, anisotropy strength andcrystal symmetry, and film crystal orientation relative to the substratenormal. We find that the contact point retraction rate can be well described bya power-law, $l \sim t^n$. Our results demonstrate that the exponent $n$ is notuniversal -- it is sensitive to the Young's angle $\theta_i$ (and insensitiveto anisotropy). In addition to classical wetting (where holes in a film heal)and dewetting (where holes in a film grow), we observe cases where a holethrough the film heals but leave a finite size hole/bubble between thecontinuous film and substrate or where the hole heals leaving a continuous filmthat is not bonded to the substrate. Surface energy anisotropy (i) increasesthe instability that leads to island break-up into multiple islands, (ii)enhances hole healing, and (iii) leads to finite island size even under someconditions where the Young's angle $\theta_i$ suggests that the film wets thesubstrate.

Sharp interface model for solid-state dewetting problems with weakly anisotropic surface energies