THEORETICAL STUDY ON CONVERAGE DEPENDENCE OF BONDINGMECHANISM AND WORKFUNCTION ALKALIMETAL / METAL SURFACE

在本项目中，我们从理论上研究了碱原子吸附金属表面的键合机制的覆盖依赖性和功函数。所采用的模型是一种考虑了原子轨道间非正交性和吸附质构型随机性的LCAO模型。非正交性对于估计共价的程度是必不可少的，并且已经表明随机性对上覆带的形成起着重要作用，并且是工作函数的温度依赖性的主要原因。1992-1993年，我们研究了附着原子之间有效相互作用的覆盖依赖性。到目前为止，在大多数理论中，相互作用仅限于静电作用，然后变成排斥作用。然而，自几年前以来，由于LEED和EELS实验，在某些情况下，相互作用在更高的覆盖率下变得有吸引力。除了静电相互作用外，我们还提出了由原子间电子转移引起的另一种相互作用，称为“内聚相互作用”。通过合理的参数设置，得到了有效相互作用在较高的覆盖范围内具有吸引力的结果。(发表于《物理学报》。B) 1993年，我们尝试将多年来建立的现有模型和方法应用于“两层吸附”问题。该系统被认为是碱金属（第1类）/碱金属（第2类）/金属。日本北海道大学的一个研究小组研究了这个问题，并获得了一些有趣的结果，包括一种可能的新催化机制。到目前为止，我们已经建立了必要的公式，并得到了一些初步的计算结果。

In this project, we have theretically investigated the coverage dependence of the bonding mechanism and the workfunction for alkali-atom adsorbed metal surface. The employed model is a type of the LCAO model in which the nonorthogonality between atomic orbitals and the randomness of the adsorbate configuration are taken into consideration. The nonorthogonality is essential to estimate the degree of covalency and it has been shown that the randomness plays an essential role on forming of the overlayr band and is a dominant origin of the temperture dependence of the workfunction.In 1992-1993, we investigated the coverage dependence of effective interactions between adatoms. In most theories, so far, the interaction is confined to the electorstatic one and then becomes repulsive. Since several years ago, however, it is suggested due to the LEED and EELS experiments that the interaction becomes attractive at higher coverages in some case. we have taken another interaction caused from the electron transfer between the adoatoms, which is called 'cohesive interaction', besides the electrostatic interaction. As a consequence, we obtained the result that the effective interaction becomes attractive at higher coverage by assuming reasonable values of parameters. (published in Phys.Rev.B)In 1993, we have try to investigate apply tha present model and method established for these years to the problem of 'two-layr adsorption'. The system considered denoted as alkali-metal(type 1 )/alkali-metal(type 2)/metal. A research group in Hookaido University have investigated this subject and obtained some interesting results including a possible new catalysis mechanism.Up to the present time, we have constructed the requisite formulation and obtained some preliminary calculated results.