Although John Cahn was known primarily as a materials theorist, he was an early adopter of computational modeling as a tool to gain insight into physical phenomena. Collaborating with a number of computational scientists and applied mathematicians, John was particularly invested in phase field models (based of course on the Cahn-Hilliard and Allen-Cahn models) and in molecular dynamics simulations (mainly for grain boundary and dislocation physics). In this talk, we will present a few results from molecular dynamics simulations that we think might have interested John. In particular, we will discuss how two sets of Shockley partial dislocations, with the same Burgers vectors, gliding on the same plane under the same physical conditions, can evince fundamentally different temperature dependence of motion. The results elucidate the thermal behavior of faceted, incoherent twin boundaries.