Entropy, dynamics, and freezing of CaSiO3 liquid

We present first principles predictions of the absolute entropy a silicate liquid (CaSiO3) over wide pressure-temperature range encompassing Earth’s mantle (2000–6000 K, 0–270 GPa). The results are derived from molecular dynamics simulations based on density functional theory and two-phase thermodynamic (2PT) method, which divides vibrational states into solid-like gas-like parts, we describe in detail. heat capacity agrees well with experimental measurements at low pressure. find that contribution accounts for more than 75% total our study. two-body approximation to excess (relative ideal gas), is computed knowledge only radial distribution function, excellent most considered, except lowest pressures temperatures. also compute CaSiO3 perovskite use solid phases determine their free energies melting curve. curve experiment independent theoretical determinations Clausius-Clapeyron integration ZW showing temperature 5600 K core-mantle boundary. nearly universal scaling self-diffusion coefficients D?=0.9exp1.2Sex, where D* coefficient suitably non-dimensionalized using macroscopic properties, Sex units Boltzmann constant per atom. estimate an isentropic, molten Earth, finding 4.4 kJ/kg/K be completely molten, producing boundary 6000 K.