Molecular Dynamics Simulation of Surface Problems (Materials Research)

该奖项支持一项合作研究计划，该计划涉及圣地亚哥加州大学的Ivan K. Schuller教授和圣地亚哥智利天主教大学的Ricardo Ramirez教授。本项目利用现代计算技术研究薄膜和表面物理领域的各种问题，包括不同晶体类型（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。利用分子动力学的计算技术求解外延生长体系表面的运动方程。外延系统将包括bcc衬底上几个原子层的文字模型和相关的电位分布，结合生长的fcc层的模型。特别注意的是开始方向对最终结果的影响。通过建立一个表面电位分布近似于镍的稳定fcc晶体模型来探讨氢的表面行为问题。然后允许单个氢原子通过适当选择的电位与该晶体相互作用，并分析组合系统的MD以研究扩散特性，地下位置的能量分布和动力学。本研究代表了计算机建模，特别是分子动力学方法在凝聚态物理中一类重要问题的应用。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，这个问题的理论方法很少。每位研究人员都为这项研究带来了互补的优势，他们拥有来自美国的实验和模拟专业知识，以及来自智利的理论专业知识。数值计算将在美国和智利进行，计算机代码的要素将共同开发。所要研究的问题具有相当的科学和技术重要性，模拟结果应作为理论测试和指导今后的实验。

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.