where 𝜑 𝑖 is the fugacity coefficient of component 𝑖, 𝑦 𝑖 is the molar fraction of component 𝑖, 𝑃 is the pressure in atm. We employed the fugacity coefficients calculated by Cooper and Shaw et al. for hydrogen and by Cooper and Newton for nitrogen and ammonia. 𝜑 H 2 = exp {exp(-3.8402𝑇 0.125 + 0.541) 𝑃 -exp(-0.1263𝑇