NiTi合金的第一性原理研究

A first principles investigation on NiTi alloy

采用第一原理平面波方法,计算了NiTi合金B2相的体相性质,如晶格常数,形成能和结合能,弹性常数,计算的结果和实验数据以及别人的计算结果符合得很好.其次,计算了NiTi(100),(110)表面的几何结构和电子结构,计算结果表明,(100)表面具有表面振荡现象,(110)表面产生了表面波纹,最外层的Ti原子相对理想表面向真空层移动了0.198,Ni原子向表面内移动了0.122.比较表面的电子结构,NiTi(100)表面Ti端位较Ni端位更容易发生反应,而(110)表面较体相更稳定.

A first principles plane-wave method is utilized to investigate the bulk properties of the NiTi alloy,such as the lattice parameters,formation energy and cohesive energy and the elastic constant.The results are in good agreement with experimental and other theoretical results.Furthermore,we have studied the geometric and electronic structures of NiTi（100） and（110）surfaces.As to the surface geometry,there are different relaxations in the surface layers.As for the cleaned NiTi（110） surface,outermost surface layer shows a large rippled relaxation in which Ni atoms contract into the bulk by 0.198 and Ti atoms expand to the vacuum by 0.122.The calculation of the surface electronic structure shows that Ti-terminated surface is more reactive than Ni-terminated surface on（100） surface and the NiTi（110） surface is inert.