An efficient method for phase-behavior calculations and its application to modeling phase-transition kinetics

Evaluation of multiphase thermodynamic properties is a critical component for simulating the kinetics of phase transitions at high pressures and temperatures under dynamic compression. It requires iterative equation-of-state (EOS) calculations to determine pressure, temperature and phase volumes and energies given the total volume, internal energy, and phase fractions. The phase-transition kinetics model reported by Myint et al. (2020) employs a semi-analytical approach to map the general EOS onto an analytically inversible (AI) EOS and obtain the pressure and temperature analytically. Here, we develop an alternative approach based on the Newton-Raphson (NR) method. The NR-EOS computation is coupled with our phase-transition-kinetics code to simulate solidification processes of water and gallium under dynamic compression. We find that the NR-EOS approach exhibits faster solution convergence than the AI-EOS method, especially for modeling of solidification kinetics in large, multidimensional systems. If time permits, other numerical considerations (timestep controls, numerical stability for ALE problems) will be presented as well. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.