Molecular Dynamics Simulation of Surface Problems (Materials Research)

该奖项支持加州大学圣地亚哥分校的伊万·K·舒勒教授和圣地亚哥智利天主教大学的里卡多·拉米雷斯教授参与的合作研究项目。该项目涉及使用现代计算技术来研究薄膜和表面物理领域的各种问题，包括不同类型的晶体(面心立方(FCC)和体心立方(BCC))的外延生长，以及过渡金属表面吸氢的能量学和动力学。外延生长系统表面的运动方程将使用分子动力学(MD)的计算技术来求解。外延系统将由体心立方衬底的顶层几个原子层的字面模型和相关的电势分布组成，并结合体心立方衬底的生长模型。将特别注意起始方向对最终结果的影响。氢的表面行为问题将通过建立一个稳定的面心立方晶体的模型来解决，该模型将给出一个近似于镍的表面电势分布。然后，单个氢原子将被允许通过适当选择的势与该晶体相互作用，并将分析组合系统的分子动力学，以研究扩散特性、亚表面位置的能量分布和动力学。这项研究代表了计算机模拟，特别是分子动力学方法在凝聚态物理中的一类重要问题上的应用。外延晶体生长的模拟可能具有重要的意义，例如，在新的半导体材料和器件的生产中，然而关于这个问题的理论方法一直很少。每个研究人员都为这项研究带来了互补的力量，美国的实验和模拟专业知识以及智利的理论专业知识。数值计算将在美国和智利进行，计算机代码的元素将联合开发。所要研究的问题具有相当大的科学和技术意义，模拟结果应该是对理论的检验和对未来实验的指导。

This award supports a cooperative research program involving Professor Ivan K. Schuller of the University of California, San Diego, and Professor Ricardo Ramirez of the Pontifical Catholic University of Chile, in Santiago. The project involves use of modern computational techniques to study a variety of problems in the fields of thin film and surface physics, including the epitaxial growth of different crystal types (face centered cubic (fcc) and body centered cubic (bcc)), and the energetics and kinetics of hydrogen absorption on the surfaces of transition metals. The equation of motion of the surface of an epitaxially growing system will be solved using the computational technique of Molecular Dynamics (MD). The epitaxial system will consist of a literal model of the top few atomic layers of a bcc substrate and the related potential distributions, combined with a model of the growing fcc layers. Particular attention will be paid to the effect of the starting orientation on the final results. The hydrogen-surface behavior problem will be approached by setting up a model of a stable fcc crystal which will be given a surface potential distribution approximating that of nickel. A single hydrogen atom will then be allowed to interact with this crystal via a suitably chosen potential and the MD of the combined system will be analyzed to study diffusion properties, the energy distributions at subsurface sites, and kinetics. This study represents an application of computer modeling, in particular the Molecular Dynamics method, to a class of important problems in condensed matter physics. The simulation of epitaxial crystal growth could have important implications, for example, in the production of new semiconductor materials and devices, yet theoretical approaches to this problem have been sparse. Each of the investigators brings complementary strength to this research, with experimental and simulation expertise from the U.S. and theoretical expertise from Chile. Numerical calculations will be performed in both the U.S. and Chile, with elements of computer codes developed jointly. The problems to be studied are of considerable scientific and technological importance, and the simulation results should be useful as tests for theories and guidelines for future experimentation.