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Recently, a first-order phase transition is predicted to occur in liquid carbon using atomistic simulation and Brenner’s bond order potential. There are also experimental data suggesting a possibility for a first-order phase transition. In light of this, a thermochemical equilibrium code (CHEQ) is used to provide guidance to experiments to find a liquid-liquid phase change in carbon foam and carbon-rich aerogel, resorcinol formaldehyde. Isotherms and Hugoniots are computed using the model of carbon by van Thiel and Ree. The present calculations predict the liquid-liquid-graphite triple point to be at 5000 K and 5.2 GPa and its critical point to be at 6000 K and 8.8 GPa. The Hugoniot calculations suggest that the liquid-liquid phase transition may be detected by performing a shock experiment with initial density of approximately 0.15 g/cm3.

Statistical‐mechanical chemical equilibrium calculations have been performed to determine the deviation of the unlike species potential from that predicted by the Lorentz‐Berthelot rule. The potentials of the water‐water and nitrogen‐nitrogen interactions have been reexamined in the light of remaining deviations from experiment. The resulting deviation of the constant from one (1), in the extended Lorentz‐Berthelot rule, is determined from the best exp‐6 potentials for nitrogen and water with consideration of possible deviations of the measured detonation velocity of RX‐23‐AB from its ideal equilibrium value.

Dynamic equation‐of‐state data for liquid CO were measured in the shock pressure range 5‐70 GPa (50−700 kbar) using a two‐stage light‐gas gun. The liquid was shocked from initial state near its saturation curves at 77 K for CO. The data were examined by using three theoretical models: (1) chemically nonreactive model, (2) a quasi‐chemicl‐equilibrium model that allows CO to dissociate into gaseous species and graphite, and (3) a chemical‐equilibrium model that also includes a dense carbon phase which exists at higher pressures and temperatures than graphite. This dense phase is assumed to be diamond. Our analysis shows that a low pressure, chemical equilibrium takes much longer than a typical shock passage time. As a consequence, the experimental data initially follow the nonreactive Hugoniot to pressures well beyond the chemical dissociation limit. Both the experimental data and the Hugoniot computed with case (3) agree satisfactorily at high pressure. Further consequences of these observations to high‐explosive studies are discussed. The experimental and theoretical details concerning this work have been published.