“…Thus, the pressure in the grand canonical ensemble serves as basic quantity for the description of the thermodynamics of plasmas. [ 19,23,25,28,41–44 ] From this follows, the expression for the densities () is given as Within a quantum statistical approach using the method of Green's functions, typical approximations of the pressure of plasmas consist of three main contributions stemming diagrammatically in the lowest approximation from the free diagrams, the ring diagrams, and the ladder diagrams, [ 9 ] which represent the contributions of free states, modified by screening, and by the contribution of bound states, respectively, At higher temperatures, we may neglect the contributions of bound states completely and approximate the pressure by we are denoting this as a Debye‐like approach. In the grand canonical ensemble, we find the pressure contributions stemming from free and ring diagrams [ 9,25,28 ] : The main nonideality term comes from ring diagrams depending on the fugacities instead of densities and correspondingly is the grand canonical Debye screening parameter.…”