STUDY ON PHASE TRANSITION OF Si (111) 7x7 STRUCTURE BY MONTE-CARLO SIMULATION

<1>7 x7结构的建模表面结构是根据每个单元的两种状态来描述的，每个单元被定义为7 x7单元的三角形的一半。这两种状态，一种是层错结构，另一种是“1x 1”结构，在格子气模型中用一个数算符表示。系统的哈密顿量由数算子的泛函给出。导出了7 × 7结构中各组分的相互作用与形成能之间的关系，并发现了一种三体相互作用的存在。考虑到“1x 1”结构是一组无序态，我们引入了简并度。<2>数值计算我们通过Monte-Calro模拟对上述模型进行了数值计算。结果表明：（1）结构经历了与实验相同的一级相变;（2）淬火表面上的F台阶、U台阶、平台生长模式的特征得到了很好的再现;（3）淬火表面上形核临界尺寸与温度的关系与实验结果定性一致。<3>结果的发表上述结果是通过各种试验得到的。每个阶段的研究结果发表在福冈工业大学的研究公报上，并在日本物理学会的几次会议上报告。现在，我们准备向某个科学期刊提交一篇包含这些新结果的论文。

<1> Modeling of 7x7 structureThe surface structure is described in terms of two states of each unit which is defined as a triangular half of the 7x7 unit cell. The two states ; one a stacking-faulted structure and the other '1x1' structure, is expressed by a number operator in the lattice gas model. The Hamiltonian of the system is given by a functional of the number operators. We derive relations between the in interactions and formation energies of components of 7x7 structure and find existence of a type of three-body interaction. Considering the '1x1' structure a set of disordered states, we introduce the degeneracy.<2> Numerical calculationWe performed numerical calculations for the above model by Monte-Calro simulation. It results that(1) the structure undergoes the first order transition as the experiments (2) the characteristic features of growing patterns from F-step, U-step, terrace on the quenched surface are well reproduced (3) the temperature dependence of the critical size for nucleation on the quenched surface is qualitatively in agreement with the experimental result.<3> Publication of resultsThe above results have been got by various trials. The result in each stage was published in reported in Research Bulletin of Fukuoka Institute of Technology and reported in several meetings of Physical Society of Japan. Now, we are going to submit a paper which include the new results to some scientific journal.