复杂轻金属氢化物的第一性原理研究-材料物理与化学专业论文.docxVIP

II II Abstract Growing concern about the future nonavailability and environmental pollution of fossil energy has led to the search of alternative fuels. Hydrogen is one possible energy carrier that could one day replace fossil fuels. One of the most daunting challenges for widespread use of H2 as a fuel is the absence of a commercially viable H2 storage technology. The relatively advanced storage methods such as high-pressure gas or liquid cannot fulfill future storage goals. Hydrogen forms metal hydrides with some metals and alloys leading to solid-state storage under moderate temperature and pressure, which has the important safety advantage over the gas and liquid storage methods. Intensive research has been done on metal hydrides recently for improvement of hydrogenation properties. Practical hydrogen storage materials must not only exhibit favorable thermodynamic properties but also have sufficiently rapid hydrogenation/dehydrogenation kinetics. The work presented in this paper is limited to identifying materials for reversible H2 storage with acceptable reaction thermodynamics. Our focus on thermodynamics is motivated by the observation that the reaction kinetics of light metal hydrides can, at least in principle, be significantly accelerated by using catalysts or by controlling the particle size of reactants. The present dissertation has investigated hydrogen-storage capacity, crystal and electronic structure, and thermodynamic properties of complex light metal hydrides. The main contents of this dissertation are as following: The thermodynamic and electronic properties of LixNa1?xMgH3 (x = 0, 0.25, 0.5 and 0.75) have been investigated using the density functional theory within the generalized-gradient approximation. The obtained cohesive energies indicate that the stability of crystal increases with increasing Li element in LixNa1?xMgH3. The reaction enthalpies for LixNa1?xMgH3 phases have been investigated along four possible dehydrogenation reaction pathwa