(湖南大學(xué) 物理與微電子科學(xué)學(xué)院，長(zhǎng)沙 410082)
摘 要: 應(yīng)用第一性原理密度泛函理論系統(tǒng)研究氧、氫和碳原子在α-鈾(001)表面的吸附與擴(kuò)散特性。研究發(fā)現(xiàn)：在鈾表面氧原子與氫原子擇優(yōu)吸附在H2位置，碳原子傾向于占據(jù)在H1位置；氧原子在鈾表面的擴(kuò)散勢(shì)壘較低，容易在鈾表面上擴(kuò)散，形成表面氧化層；氫原子的擴(kuò)散勢(shì)壘較高，碳原子的擴(kuò)散勢(shì)壘最大，難以在表面擴(kuò)散。吸附原子從鈾表面向次表面層擴(kuò)散時(shí)，氧原子的擴(kuò)散勢(shì)壘很高，難以向次表面擴(kuò)散；碳和氫原子的擴(kuò)散勢(shì)壘較低，特別是在氧的輔助作用下，碳原子向次表面的擴(kuò)散勢(shì)壘降低約0.5 eV，使碳原子易于向次表面層擴(kuò)散；鈾表面上會(huì)形成氧化層，次表面會(huì)形成富碳層，可對(duì)鈾的進(jìn)一步氧化起到抑制作用，這與相關(guān)實(shí)驗(yàn)結(jié)果符合較好。
關(guān)鍵字: α-鈾；第一性原理；表面吸附；擴(kuò)散勢(shì)壘
（School of Physics and Microelectronics, Hunan University, Changsha 410082, China）
Abstract:The adsorption and diffusion properties of O, H and C atoms on α-U(001) surface were studied by first-principles density functional theory approach. For the on-surface adsorption, O and H atoms prefer to occupy the H2 site, while C atoms tend to occupy the H1 site. The diffusion barrier of O atom on U surface is low and the diffusion is easy, which will lead to the formation of uranium-oxidation layer on the top of surface. The diffusion barrier of H atom is larger and that of C atom is the largest one, thus it is difficult for C atom diffusion on the U surface. As for the diffusion of atom from the surface site to the sub-surface, the barriers of H and C atoms are low, while that of O atom is very high, which indicates that the O atom can not migrate into the next surface. And the barrier of C atom diffusion to the sub-surface is reduced by about 0.5 eV with the assistance of O atom nearby. The U-O oxidation layer on the surface and the U-C layer on the sub-surface can be formed easily, which help to prevent the metallic U from further oxidation. These results agree good with available experiments.
Key words: α-uranium; first-principles; surface adsorption; diffusion barrier
