摘要
本文采用Sulston等人所发展的一维紧束缚半无限无序二元合金模型和格林函数方法,分别利用相关势近似(CPA)和平均T矩阵近似(ATA)计算了氢原子在无序二元合金Ni_xCu_(1-x)、Au_xPt_(1-X)和Ni_xP_(1-x)表面上的化学吸附能。给出了化学吸附能与合金的浓度百分比之间的关系曲线。结果表明:(1)H在Ni_xCu_(1-x)合金表面上的化学吸附随合金中Ni的含量的增加愈加稳定;(2)H在Au_xPt_(1-x)合金表面上的化学吸附在Au的含量为25％(Pt的含量为75％)时最稳定;(3)H在Ni_xPt_(1-x)合金表面上的化学吸附在Ni与Pt的含量比例为2:8时最不稳定。计算还表明,采用相关势近似和采用平均T矩阵近似所得的结果吻合得相当好。因此用非自洽的平均T矩阵近似也能正确处理无序二元合金表面上化学吸附能的计算问题。
The one-dimensional tight-binding model and the Green's function (GF) method are used to calculate the chemisorption energy (△E) of a H atom on semi-infinite disordered binary al- loys (SDBA) (NiCu, AuPt, NiPt) within the coherent-potential approximation (CPA) and the average T-matrix approximation (ATA). The chemisorption energy is calculated as a function of the concentration percentages of the two components of DBA. The results are as follows: (I) for the system of H / Ni_xCu_(I-.x), △E decreases with the increasing of the Ni Concentra- tion x, resulting in a more stable chemisorption, (Ⅱ) for the system of H / Au_xPt_(I-x), H is preferentially adsorbed on a AuPt DBA at the concentration ratio of 25 : 75, (Ⅲ) for the system of H / Ni_xPt_(I-x), the most unstable chemisorption occures at the concentration ratio of 20 : 80. The calculation also shows that the results obtained by ATA are as good as those by CPA.
