Computer Simulation Study Of The Mechanical Behavior Of Hhdrogen Molecular Crystal

With the fast reduction of non-renewable energy on earth, the utilization and lucubrating of nuclear energy has became one of the important national strategic deployment of thesocial stability and long-term economic growth. Nuclear energies mainly include fission and fusion energy. The current nuclear energy installations in the world which can output stablely is nuclear fission reactor, but it is unsafe and unfriendly to the environment. So the nuclear fusion is currently the research hot-spot of major countries in the world. The inertial confinement fusion(ICF) is an important embranchment of nuclear fusion. The ICF fusion energy is obtained by nuclear fusion reactions that are initiated by the irradiation of high energy laser or particle beams on a deuterium-tritium(D-T) fuel pellet. The fusion reaction and the energy ouput depend on whether the design of the pellet is reasonable or not. The study of the mechanical behavior of hydrogen molecular(H2) crystals, is of significance to the accurate design and the grow of the pellet crystal. The stable crystal structure and mechanical properties of H2 cyrstals have been systematically studied and analyzed using the ab initio software package VASP in this paper. The main results for our study are as follows:First. VASP software package has been performed to study the specific crystal structure, especially the axial relative position in hydrogen molecules crystal. The results show that Pa3 structure is the most stable crystal structure of fcc hydrogen crystal and the disordered structure is the most stable crystal structure of hcp hydrogen crystal.Second. VASP software package has been performed to study the binding energy of fcc and hcp hydrogen crystals. The research results in this paper show that the binding energy of fcc hydrogen molecular crystal is higher than that of hcp hydrogen molecule crystal, which suggestes that the face-centered cubic hydrogen molecular crystal is more stable.Third. During the study of the inner structure of molecular hydrogen crystal, the effect of zero-point-energy has been considered. Eventually, the results show that the effect of zero-point-energy is obvious and shouldn’t be ignored. We think this is because the quality of hydrogen is the most small among all elements, and the zero-point vibration of hydrogen is very obvious.Forth. Most of the VDW correction methods in VASP package were performed in the calculations of fcc and hcp hydrogen molecular crystal. The results show that all the VDW correction methods overestimate the intermolecular force between hydrogen melocules in the hydrogen melocular crystal, resulting in the decrease of lattice constances, which declares that the VDW correction methods in VASP package is not suitable for the hydrogen molecular crystal.Fifth. VASP software package has been performed to study the elastic properties of fcc and hcp hydrogen crystals. The elastic constants of the fcc hydrogen molecular crystal and hcp hydrogen molecular crystal, are accorded with the requirement of the structural stablity according to the strain energy theory, indicating the two kinds of structures of hydrogen molecular crystals are stable.Sixth. According to the elastic constants, we calculated the mechanical modulus of fcc and hcp hydrogen crystals. Comparing the mechanic constants of the two kinds of hydrogen molecular crystal, we found that the extrusion resistance, shearing resistance and deformation resistance of the hydrogen molecular crystal are stronger than the hcp hydrogen crystal.