Thermodynamic properties and plasma phase transition in dense hydrogen mixtures

Summary form only given. The internal energy and equation of state of dense hydrogen and hydrogen-helium mixture are investigated by direct path integral Monte Carlo method which are further improved in comparison to our previous results. Data for four isotherms T=10,000 K, 30,000 K, 50,000 K and 100,000 K are presented. For T=10,000 K it is shown that the internal energy is lowered due to droplet formation for densities of the order 10/sup -23/ cm giving direct support for the existence of a plasma phase transition in megabar hydrogen. The thermodynamic properties of warm dense matter, such a hydrogen and hydrogen mixture at megabar pressure, are essential for the description of plasmas generated by strong lasers, ion beams or free electron lasers. Among the phenomena of particular current interest are the high-pressure compressibility of deuterium, metalization of hydrogen, Wigner crystallization plasma phase transition etc., which occur in situations where both interaction and quantum effects are relevant and a crossover from a neutral system to full ionization takes place. We use the direct fermionic path integral Monte Carlo simulations to investigate the dense plasmas in a wide range of densities and temperatures.