单个钛原子储氢能力和储氢机制的第一性原理研究

A first-principles study of capacity and mechanism of a single titanium atom storing hydrogen

采用基于密度泛函理论的第一性原理方法研究了单个过渡金属钛原子吸附氢分子的物理机制.研究表明,单个钛原子最多能吸附8对氢分子,吸附结构为对称的两个类金字塔型结构,其平均吸附能为-0.28 eV通过计算轨道能级和差分电荷密度分布,分析决定吸附结构、吸附能大小以及吸附氢分子数目的内在物理机制.研究表明,钛原子的4s电子转移到3d轨道上,从而产生较强的极化电场,导致氢分子极化,钛原子通过静电极化作用吸附氢分子.本文的研究将对设计高密度储氢材料有一定的指导作用.

Using the density functional theory of first principles,we investigate the binding mechanism of a single transition metal atomtitanium adsorbing hydrogen molecules.We find that a single titanium atom can absorb eight hydrogen molecules.The hydrogen molecules around Ti atom form two symmetrical pyramid-like structures with an average adsorption energy of-0.28 eV.By calculating the orbital energie and the distribution of differential charge density,we analyse the intrinsic physical mechanism of determining adsorption structure,adsorption energy and hydrogen storage capacity.The results show that a 4s electron of a titanium atom transfers to the 3d orbit,which can produce a strong polarization electric field,resulting in polarization of the hydrogen molecules.Therefore,the titanium atom adsorbs hydrogen molecules by electrostatic polarization.Our results will present a guidance for designing high-density hydrogen storage materials.