Equilibrium molecular dynamical simulations of three-dimensional (3D) Yukawa fluids are performed to investigate thermodynamics and supercritical transition of 3D dusty plasma fluids. The normalized reduced excess entropy $s_{\mathrm{ex}}/s_{\mathrm{ex}}^{\mathrm{m}}$ of 3D Yukawa fluids (where $s_{\mathrm{ex}}^{\mathrm{m}}$ is the excess entropy at the melting point) is calculated from their reduced excess internal energy $u_{\mathrm{ex}}$, so that different variation trends of $s_{\mathrm{ex}}/s_{\mathrm{ex}}^{\mathrm{m}}\propto {\mathrm{\Gamma }}^{0.5}$ and $\propto {\mathrm{\Gamma }}^2$ are obtained at lower and higher temperatures, respectively. A fitting expression for $s_{\mathrm{ex}}/s_{\mathrm{ex}}^{\mathrm{m}}$ of 3D Yukawa fluids for all temperatures is proposed here, leading to the general expression of the excess internal energy. The relative deviation of $s_{\mathrm{ex}}/s_{\mathrm{ex}}^{\mathrm{m}}$ with respect to the power law scaling is introduced as $\mathrm{\Delta }$, so that the criterion of $\mathrm{\Delta }=10\%$ is proposed to determine the supercritical transition of 3D Yukawa fluids between the liquidlike and gaslike states. It is found that the supercritical transition points of 3D Yukawa fluids identified from $\mathrm{\Delta }=10\%$ well agree with the previous results from other criteria.

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• Dusty or complex plasma
• Single-component plasmas
• Strongly-coupled plasmas