类金刚石薄膜sp^2-sp^3轨道杂化的第一性原理研究

First-principles studies of sp^2-sp^3 hybridized bonding in diamond-like films

以强σ键连接的sp2和sp3杂化碳饱和簇模型,即金刚石和石墨两相和团簇模型为研究对象,通过分子结构、电荷分布、能带结构、电子态密度和分子轨道的第一性原理计算和分析,研究了类金刚石薄膜中sp2-sp3轨道杂化的空间结构稳定性的成键特性等.结果表明,成键过程中由于微扰作用破坏了原子内部"吸引"与"排斥"的平衡关系,使电子云重新分布,而键能大小和电子云的重叠密切相关,因而两相共存对电荷分布和结构均有影响.能带结构分析发现sp2杂化C原子将π键引入,产生π和π*能带使带隙变窄,说明类金刚石薄膜的半导体本质.电子态密度计算结果中费米能级附近出现杂质峰,说明存在中间杂化和/或π态和σ态的转化.

Saturated cluster models of the diamond phase and graphite phase coexistence,i.e,sp2 hybridized carbons and sp3 hybridized carbons connected by strong σ bonds,were calculated and analyzed by first principles.Comparing the molecular structures,molecular orbits,band structures,and density of states,we analyzed the effect of sp2-sp3 hybridized bonding in diamond-like carbon films on space structures and bonding properties.It is found that the balance between ＂repulsive＂ and ＂attractive＂ in atoms were destroyed by σ bonds,and charges redistributing arose bond energy change,as a result,charges and space structures were effected by coexistence of the diamond and graphite phases.Band structures indicated that diamond-like carbon films were semiconductor because sp2 hybridize importedπbonds and produced π,π＊ bands,resulting in the aecrease of band gaps.Density of states studied in this work discovered impurity near Fermi energy,indicating midway hybridized and/or transitions between π states and σ states.