金属Fe与间隙H原子相互作用的密度泛函研究

First principles investigation of interaction between interstitial hydrogen atom and Fe metal

采用基于密度泛函理论的第一性原理方法,研究了不同摩尔比下H在α-Fe和γ-Fe晶格中的间隙占位情况,计算了稳态晶体的总能量、结合能、溶解热、电子态密度、电荷差分密度和电荷布居,分析了间隙H原子和Fe晶格之间的相互作用,讨论了H溶解对α-Fe和γ-Fe晶体电子结构的影响.结果表明:H溶解引起α-Fe和γ-Fe晶体点阵晶格畸变,体积膨胀率随着溶氢量的增加而增加.从能量角度分析发现,H优先占据α-Fe的四面体间隙位,而在γ-Fe中优先占据八面体间隙位.态密度、电荷差分密度以及电荷布居分析发现,间隙H原子与Fe晶格的相互作用仅由H的1s轨道电子和Fe的4s轨道电子所贡献,二者作用力相对较弱,这是造成H在Fe晶格中固溶度较低的主要原因之一.

In this paper, the site occupations of H under different mole ratios in interstitials of α-Fe and γ-Fe are studied by the first principles method based on the density functional theory. The total energy of the steady state crystal, binding energy, solution heat, density of states, charge density difference and charge population are calculated. The interaction between interstitial H and Fe lattice is analyzed. The influences of hydrogen dissolution on electronic structure of α-Fe andγ-Fe are discussed. The results show that the dissolved hydrogen leads to the lattice distortions ofα-Fe andγ-Fe, and the volume expansion ratio increases with the dissolved quantity of hydrogen increasing. The energy analysis indicates that the hydrogen preferentially occupies the tetrahedral interstitial ofα-Fe, while in theγ-Fe it preferentially occupies the octahedral interstitial. The analyses of density state, charge density difference and charge population reveal that the interaction between interstitial hydrogen and Fe lattice is contributed by the H 1s orbital and Fe 4s orbital, and this interaction is relatively weak, which is one of the main reasons for lower solid solubility of hydrogen in Fe lattice.