ITR-(ASE)-(sim): Ab Initio Modeling of Self-Assembled Pattern Growth in Heteroepitaxial Alloy Films with Long-Range Elastic interactions

该奖项是根据信息技术研究招标NSF-04-012下提交给材料研究部的提案而授予的。该奖项涵盖的研究活动属于国家优先领域“科学与工程进展”和技术重点领域“计算建模或模拟研究中的创新”。该奖项支持计算研究和教育，以开发模拟算法，目的是研究合金薄膜中的模式形成，可用于纳米结构的定向自组装。在几种由非混相合金组成的表面合金薄膜中，自发形成了二维（2D）纳米图案（条纹和圆盘）。这些系统在长度尺度上表现出规则的特征，目前即使是最先进的光刻技术也无法实现，这显示出在纳米级器件的定向自组装中使用掩膜的前景。通过计算机模拟，PI将研究在超薄合金薄膜生长过程中条纹和圆盘的规则阵列的形成。PI的研究目标是在以下关键方向上取得重大科学进展：具有形成长周期有序图案的强能量倾向的新合金/衬底体系的鉴定，可作为定向自组装的掩膜。开发超薄膜外延生长的模型，可以预测实现稳健和高度规则模式的最佳参数。开发有效的计算算法来模拟具有远程弹性相互作用的表面系统。PI将使用一系列计算研究工具，从从头算电子结构计算到基于晶格的长距离弹性相互作用的动力学蒙特卡罗（KMC）模拟。目的是建立超薄异质外延表面合金薄膜中图案形成的热力学和动力学的定量模型。热力学模型将用于系统地搜索合金系统，表现出能量倾向，形成纳米尺度的周期性图案。除了纯粹的理论兴趣之外，有一个强烈的实际需要来确定这样的系统，因为只有少数已知的可以形成定向自组装所需的大规模无缺陷结构的图案形成表面合金的情况。动力学生长模拟可以帮助我们控制生长阶段结构缺陷的数量。这些模型将用于预测最佳实验条件，如组成、温度和沉积速率。最后，远程弹性应变效应将用重整化群论中常见的精确粗粒化方法来处理。理论研究将与桑迪亚国家实验室进行的金属表面合金实验研究合作进行。该奖项对教育的影响更为广泛。它包括让本科生和研究生参与在材料研究中使用模拟的计算项目，为研究代码开发基于HTML和perl的Web界面，并将其用于教授相变和表面生长的热力学和动力学。Perl脚本将用于从Web表单收集输入参数，在远程LINUX服务器上启动模拟，并在动态生成的Web页面上显示结果。这种方法代表了一个有希望的未来平台，可以将现有的研究代码与教育活动相结合。获得的经验和Web脚本将与社区免费共享。该奖项是根据信息技术研究招标NSF-04-012向材料研究部提交的一份提案而授予的。该奖项涵盖的研究活动属于国家优先领域“科学与工程进展”和技术重点领域“计算建模或模拟研究中的创新”。该奖项支持计算研究和教育，以开发模拟算法，目的是研究合金薄膜中的模式形成，可以用作纳米尺度上组装材料和纳米结构的模板。在几种由非混相合金组成的表面合金薄膜中，自发形成了二维（2D）纳米图案（条纹和圆盘）。这些系统在长度尺度上表现出规则的特征，目前即使是最先进的光刻技术也无法实现，这显示出在纳米级器件的定向自组装中使用掩膜的前景。通过计算机模拟，PI将研究在超薄合金薄膜生长过程中条纹和圆盘的规则阵列的形成。除了纯粹的理论兴趣之外，有一个强烈的实际需要来确定这样的系统，因为只有少数已知的可以形成定向自组装所需的大规模无缺陷结构的图案形成表面合金的情况。动力学生长模拟还可以帮助我们控制材料和纳米结构生长过程中结构缺陷的数量。结构缺陷影响着材料和纳米结构的性能。理论研究将与桑迪亚国家实验室进行的金属表面合金实验研究合作进行。该奖项对教育的影响更为广泛。它包括让本科生和研究生参与在材料研究中使用模拟的计算项目，使研究代码更加“用户友好”，并将它们用于教授相变和表面生长的热力学和动力学。获得的经验和Web脚本将与社区免费共享

This award was made on a proposal submitted to the Division of Materials Research under the Information Technology Research solicitation NSF-04-012. Research activities covered by this award fall under the National Priority Area, "Advances in Science and Engineering," and the Technical Focus Area, "Innovation in Computational Modeling or Simulation in Research." This award supports computational research and education to develop simulation algorithms with an aim to study pattern formation in alloy films that could be used for directed self-assembly of nanostructures. Spontaneous formation of two-dimensional (2D) nanoscale patterns (stripes and disks) has been observed in several surface alloy films composed of immiscible species. These systems exhibit regular features on length scales that are currently inaccessible to even the most advanced lithographic techniques, showing promise as masks for use in directed self-assembly of nanoscale devices. Using computer simulations, the PI will study the formation of regular arrays of stripes and disks in growing ultrathin alloy films. The PI's research aims to make significant scientific advances in the following key directions:1. Identification of new alloy/substrate systems with strong energetic tendencies to form long-period ordered patterns, which could be used as masks for directed self-assembly.2. Develop models of epitaxial growth of ultrathin films that can predict optimal parameters for achieving robust and highly regular patterning.3. Develop efficient computational algorithms for simulating surface systems with long-range elastic interactions.The PI will use a range of computational research tools spanning ab initio electronic structure calculations to lattice-based Kinetic Monte Carlo (KMC) simulations with long-ranged elastic interactions. A goal is to construct quantitative models of the thermodynamics and kinetics of pattern formation in ultrathin heteroepitaxial surface alloy films. Thermodynamic models will be used to systematically search for alloy systems that exhibit energetic tendencies to form patterns with nanometer-scale periodicities. Besides pure theoretical interest, there is a strong practical need to identify such systems as there are only a few known cases of pattern-forming surface alloys that can form large-scale defect-free structures required for directed self-assembly.Kinetic growth simulations may help us to control the number of structural defects during the growth stage. These models will be used to predict optimum experimental conditions such as the composition, temperature, and deposition rate. Finally, long-range elastic strain effects will be treated by accurate coarse-graining methods familiar from renormalization group theory. Theoretical research will be performed in collaboration with experimental studies of metallic surface alloys carried out at Sandia National Labs.Education is a broader impact of this award. It includes involving undergraduate and graduate students in computational projects on the use of simulation in materials research and developing an HTML- and Perl-based Web interface for research codes and use them in teaching thermodynamics and kinetics of phase transformations and surface growth. Perl scripts will be used to collect input parameters from a Web form, launch the simulation on a remote LINUX server, and display the results on dynamically generated Web pages. This approach represents a promising future platform for integrating existing research codes with educational activities. The acquired experience and Web scripts will be freely shared with the community.%%%This award was made on a proposal submitted to the Division of Materials Research under the Information Technology Research solicitation NSF-04-012. Research activities covered by this award fall under the National Priority Area, "Advances in Science and Engineering," and the Technical Focus Area, "Innovation in Computational Modeling or Simulation in Research." This award supports computational research and education to develop simulation algorithms with an aim to study pattern formation in alloy films that could be used as a template to assemble materials and nanostructures on the nanoscale. Spontaneous formation of two-dimensional (2D) nanoscale patterns (stripes and disks) has been observed in several surface alloy films composed of immiscible species. These systems exhibit regular features on length scales that are currently inaccessible to even the most advanced lithographic techniques, showing promise as masks for use in directed self-assembly of nanoscale devices. Using computer simulations, the PI will study the formation of regular arrays of stripes and disks in growing ultrathin alloy films. Besides pure theoretical interest, there is a strong practical need to identify such systems as there are only a few known cases of pattern-forming surface alloys that can form large-scale defect-free structures required for directed self-assembly. Kinetic growth simulations may also help us to control the number of structural defects during the growth of materials and nanosctructures. Structural defects affect the properties of materials and nanstructures. Theoretical research will be performed in collaboration with experimental studies of metallic surface alloys carried out at Sandia National Labs.Education is a broader impact of this award. It includes involving undergraduate and graduate students in computational projects on the use of simulation in materials research and making research codes more "user friendly" and using them in teaching thermodynamics and kinetics of phase transformations and surface growth. The acquired experience and Web scripts will be freely shared with the community.***