where V is the volume of the simulation box, k B is the Boltzmann constant, T is the temperature, and ⟨σ xy (t)σ xy (0)⟩ is the time correlation function of the off-diagonal components of the stress tensor σ xy . This method provides a rigorous way to extract the viscosity from MD simulations by capturing the response of the system to shear stress. The experimental measurement of the viscosity is performed using the rotational method, with the equipment model Haake Rheometer Mars60, at a shear rate of 40 1/s. More details can be found in the Supporting Information. We employed a PDMS system consisting of 100 chains, each with 11 monomers, for viscosity calculations at varying temperatures. As seen in Figure , the viscosity of these shortchain PDMS systems increases as the temperature decreases, following the Arrhenius-like behaviors in the melt state. Compared with the experimental measurements, our simulation results exhibit qualitatively consistent trends while predict significantly lower viscosities. It should be noted that we are not aiming for a quantitative comparison between simulations and experiments. Due to the constraints on the spatio-temporal scale accessible by atomistic MD, simulating PDMS systems with a high molecular weight, close to those used in experiments, presents significant challenges with current computational resources. Among the force fields that have been benchmarked, the two all-atom models, namely HUANG and OPLS-AA, as well as the united-atom (UA) model, are observed to predict lower viscosities, which aligns with expectations of the molecular weight dependence for polymer viscosity.