Electrocaloric effects in monolayer germanium sulfide: A study by molecular dynamics simulations and thermodynamic analyses

In this paper, molecular dynamics (MD) simulations and thermodynamics analyses are performed to investigate the electrocaloric (EC) effect in monolayer germanium sulfide (GeS). Our MD simulations show a large EC effect in the armchair direction of monolayer GeS at room temperature, since monolayer GeS only has polarization in the armchair direction due to its anisotropic structure. Moreover, an enhancement in the EC effect is observed in monolayer GeS by increasing the ambient temperature. A thermodynamic model is proposed to explain this impact of temperature on the EC effect, which originates from the thermally enhanced thermal expansion property of monolayer GeS. Moreover, the thermodynamic model incorporated with the material parameters extracted from MD simulations is able to predict the EC coefficient. The predicted value is found to be identical to the value obtained from MD simulations, which further proves the EC effect observed in monolayer GeS. The observation of the EC effect in monolayer GeS (a typical two-dimensional material) is expected to open a new direction in searching EC materials and, meanwhile, provide opportunities for the innovative design of novel solid-state nanoscale cooling devices.