Carbon Chemical Speciation and Polymerization in Liquid Metals

Quantitative understanding of the chemical spe- ciation and thermodynamics of metal-carbon polymeriza- tions within three different liquid metals, Al, Cu, and Ag, will enable new classes of high-performance materials. Metalo- carbons, low molecular weight metal-carbon species, are identified using ab initio molecular dynamics (AIMD) by monitoring the long-time evolution of thermodynamically fa- vored species within explicit metal atom solvent. Metalocar- bons observed in AIMD agree with the structures determined by ab initio molecular mechanics and statistical thermody- namics from a density functional theory implementation of a COnductor-like State MOdel (COSMO) of solvation. The metalocarbon Gibbs energies calculated from the COSMO implicit sol- vent agree quantitatively with the Gibbs energy long-time averages computed by AIMD with explicit metal atom solvent. Thermochemical analysis predicts that metalographene structures are thermodynamically more stable than smaller metalo- carbon species, suggesting that metalocarbons can be polymerized into larger metalographenes in liquid aluminum, copper, and silver solutions. We identify the influence of charge and electric field on the metal solution reaction mechanism thermo- dynamics. Redox reactions greatly affect the step addition equilibrium constants. COSMO and AIMD predict aluminum-carbon vibrational spectra from inelastic neutron scattering (INS) within liquid metal and solid metal compositions. An experimental INS spectrum of an aluminum covetic with 3 wt% carbon matches specific aluminographenes. This novel finding provides a unique avenue for identifying different metalographene compositions within covetics and may become an important tool to develop high performance materials in many different metals.