First Principle Study Of Low-Z Warm Dense Matter

Warm dense matter(WDM)is an extreme state of matter characterized as intermediate between condensed matter,gases,and ideal plasmas.Widely existed in stars,the explosion of energetic materials,the implosion of ICF pellet,warm dense matter plays an important part in related region.It is also one of main objects of High Energy Density Physics for its complicated mircostructure and dynamic process.The strong-nonlinearity,tight coupling and partial degeneracy of electrons lead the theoretical and experimental study of warm dense matter very challenging.Herein first-principles molecular-dynamics simulations based on finite-temperature Kohn-Sham and Orbital-Free density functional theory is adopted to study the phase transition process,electron structure,X-ray absorption,ion transport property of warm dense matter,including the following aspects:1.Performed an accurate investigation on the shock compressed lithium in an attempt to clarify the long-standing confusion about the equation of state.Our results presented a smooth Hugoniot curve for the density up to 1.5 g/cm3,and then declined the existence of a'kink' in the region between about 1.2 and 1.4 g/cm3.Moreover,a simple melting behavior is also approved in corresponding to the smooth Hugoniot curve,instead of the complicated solid-to-solid and solid-to-amorphous phase transitions reported before.Furthermore,the XANES is suggested as an efficient experimental technique for demonstrating the structural evolution of the warm dense lithium along the shock Hugoniot curve.2.Simulate the stratification phenomenon of Deuterium-Tritium fuel in inertial confine-ment fusion implosions,which may cause the reduction of neutron yield.With advantage of high efficiency of orbital-free density functional theory,the supercell contains near 10 thousands of atoms.The stratifcation phenomenon is successfully observed in the simulation 3.A series of matryoshka superatoms X@Y12@X20(X=Ge,Y=Zn;X=Sn,Y=Mg,Mn,Zn or Cd;X=Pb,Y= Mg,Mn,Cd or Hg)with icosahedral symmetry has been extensively studied,to focus on the influence of the spin-orbit coupling on geometries,stabilities,electronic structures and magnetic moments for these clusters.Generally speaking,the effect of spin-orbit coupling is highly correlated with composition elements of these clusters.Ge@Zn12@Ge20 is little affected by the spin-orbit coupling,while clusters containing Sn atom will generally undergo a moderate influence on their atomization energy,HOMO-LUMO gap and projected density of states.For clusters with Pb atoms,the effect of spin-orbit coupling could be observed distinctly in most cases.Our results demonstrate that the spin-orbit coupling can play a substantial role in superatoms containing heavy elements.