Ab initio equation of state and transport properties of carbon–hydrogen–oxygen systems at extreme conditions

Carbon-based materials such as pure carbon (C), hydrocarbons (CH), and oxygen-bearing hydrocarbons (CHO) are widely used as ablator materials in inertial confinement fusion (ICF) experiments, where they are compressed to densities of several tens of grams per cubic centimeter and temperatures up to hundreds of electronvolts. To understand the thermodynamic and transport properties of these materials under such conditions, we present a first-principles study of the equation of state and electronic transport properties of C, CH, and CHO based on density-functional-theory molecular dynamics and the Kubo–Greenwood formalism over densities of 2.6−50 g/cm3 and temperatures of 1×104−1.16×106 K. Clear composition-dependent trends emerge: CH exhibits systematically higher pressures than C and CHO, while structural analysis shows that H and O progressively reduce C–C connectivity and increase chemical disorder. These structural changes directly influence electronic transport. Electrical and thermal conductivities increase with compression for all compositions, with pure C showing the largest conductivities at low temperature and high density, while CH dominates at higher temperatures once strong ionization increases the carrier density. The resulting dataset provides a consistent first-principles benchmark for C-based mixtures under ICF-relevant warm dense matter conditions.