Molecular Dynamics Study Of Hydrogen Alloy At High Pressure

As early as 80 years ago the Wigner and Huntington has predicted the existence of metallic hydrogen atoms. So far there have been a lot of research work aims to determine the crystal structures under the effect of high pressure. It was found that the high pressure in different interval(0-300GPa), hydrogen and its isotope with the different crystal structures. With the change of the pressure, there has a lot of complex structural phase transition. Combining the cluster expansion method(CEM) and the first principle of molecular dynamics method in this paper, we studied the phase change of the different structure of hydrogen deuterium alloy under high pressure and thermodynamic properties. the main research contents and innovative results are as follows:First we based on first principles method to study hydrogen and deuterium alloys structure transformation at high pressure and hydrogen or deuterium isotope effect. In the metal phase diagram, when the high pressure in the interval(110-150GPa) hydrogen crystal structures are in phase II, namely broken-symmetry phase. Studies have shown that hydrogen phase change order is C2 /c?Cmca-12?Cmca?I41/ amd(Cs-IV). Based Pca21 construction phase II of hydrogen, we studied isotope effect of hydrogen and deuterium, found in consideration of the zero-point energy, phonon effects and temperature effects,through the V-T phase diagram can be clearly observed hydrogen and deuterium isotope effects.We adopt cluster expansion method(CEM) and the first principles of molecular dynamics method to study at the 3300-4300 GPa pressure section atomic structure of hydrogen and face-centered structure of the equation of state of metallic hydrogen. And focuses on the structure of the high-pressure hydrogen, elastic constants and sound velocity mechanics parameter along with the change of the pressure. We explores the alloy shear velocity and compressed sound velocity changing with the pressure. The study found that the velocity of hybrid system between the speed of sound of pure hydrogen and pure deuterium. Shear and compression velocity are increased with the increase of the pressure. In addition LI0 structure of the alloy changed from unstable mechanical structure to a stable structure at about 4000 GPa.