The Convergence rate of the Gibbs sampler for the 2-D Ising model via a geometric bound

We study the geometric bound introduced by Diaconis and Stroock $(1991)$ of the Gibbs sampler for the two-dimensional Ising model with free boundary condition. The obtained result generalizes the method proposed by Shiu and Chen $(2015)$ from dimension one to dimension two. Furthermore we observe that the new bound improves the result given by Ingrassia $(1994)$.