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NiTi形状记忆合金作为一种广泛使用的生物医学材料,表面形成的氧化膜是其具有良好生物相容性的基础。氧分子在NiTi合金表面的吸附是其形成氧化膜的关键,应用离散变分X_α方法,首次对O_2分子在B_2结构NiTi(100)表面的吸附过程进行了理论研究,分别计算了在两种不同的O_2分子吸附方式中Ti-O原子间的键级和电荷分布。结果表明:O_2分子垂直接近NiTi(100)表面对其发生吸附更为有利。在吸附过程中,O_2分子中只有一个氧原子被其最近邻的一个表面钛原子所吸附,而合金中其它表面原子及体相原子的电子结构没有变化。Mulliken集居数及局域态密度分析表明,吸附过程中钛原子与氧原子之间的相互作用主要是由2p(O)电子和4s,4p(Ti)电子贡献。
NiTi shape memory alloy is a kind of widely used biomedical materials. The oxide film formed on the surface is the basis of its good biocompatibility. The adsorption of oxygen molecules on the surface of NiTi alloy is the key to the formation of oxide film. The adsorption of O_2 on the NiTi (100) surface of B_2 structure has been studied for the first time by using the discrete variational X_α method. O 2 Molecule Adsorption Mode for Bonds Between Ti-O Atoms and Charge Distribution. The results show that it is more favorable to adsorb O_2 molecules perpendicular to NiTi (100) surface. During the adsorption process, only one oxygen atom in O 2 molecule is adsorbed by one of its nearest neighbor titanium atoms, while the electronic structure of the other surface atoms and bulk atoms in the alloy does not change. Mulliken population number and local density of states analysis showed that the interaction between titanium atoms and oxygen atoms in the adsorption process is mainly contributed by 2p (O) electrons and 4s, 4p (Ti) electrons.