EAGER: An Atomistic-Continuum Formulation for the Mechanics of Monolayer Transition Metal Dichalcogenides

二维材料是由化学元素或元素化合物组成的，同时保持单个原子层的晶体结构。二维材料，特别是过渡金属二卤化物(TMD)，显示出巨大的潜力转化为先进的材料系统和器件，如场效应晶体管、太阳能电池、光电探测器、燃料电池、传感器和透明柔性显示器。为了在尖端应用中实现TMD的广泛应用，必须更好地了解大面积TMD的复杂变形。大面积的TMD可以通过预测建模进行模拟和分析，这是目前缺乏的一种能力。这一早期概念探索性研究奖章支持基础研究，这些研究克服了大规模原子建模的当前挑战，为包含数十亿个原子的单层TMD获得了高效但可靠的连续介质模型。该模型将是可翻译的，并将有助于纳米技术、电子和替代能源行业的广泛应用的发展。该奖项将进一步支持发展高级研究生水平的多尺度建模课程，并在两个关于二维材料力学的国际会议上组织研讨会。TMD的实验样本包含数十亿个原子，因此无法获得最先进的分子动力学模拟。此外，由于原子表面存在原子间键，现有的表面晶体弹性模型不能应用于多原子厚度的二维TMD。晶体弹性模型旨在通过将所有原子间键投射到中间表面来跟踪它们的变形来解决这个问题。因此，实际的变形键将使用中间表面的变形来计算。此外，还将推出一种技术，以结合TMD的曲率和拉伸对其与基材相互作用的影响。该模型将被用来产生对机械不稳定性和衬底相互作用对它们的作用的见解。粗粒度模型将克服分子动力学模型的计算瓶颈，模拟由数十亿个原子组成的TMDS样本。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Two-dimensional materials are made of chemical elements or compounds of elements while maintaining a single atomic layer crystalline structure. Two-dimensional materials, especially Transition Metal Dichalcogenides (TMDs), have shown tremendous promise to be transformed into advanced material systems and devices, e.g., field-effect transistors, solar cells, photodetectors, fuel cells, sensors, and transparent flexible displays. To achieve broader use of TMDs across cutting-edge applications, complex deformations for large-area TMDs must be better understood. Large-area TMDs can be simulated and analyzed through predictive modeling, a capability that is currently lacking. This EArly-concept Grant for Exploratory Research (EAGER) award supports fundamental research that overcomes current challenges in large-scale atomistic modeling to obtain an efficient but reliable continuum model for single-layer TMDs containing billions of atoms. The model will be translational and will contribute towards the development of a wide range of applications in the nanotechnology, electronics, and alternative energy industries. The award will further support development of an advanced graduate-level course on multiscale modeling and organization of symposia in two international conferences on mechanics of two-dimensional materials.Experimental samples of TMDs contain billions of atoms and hence are inaccessible to the state-of-the-art molecular dynamics simulations. Moreover, existing crystal elastic models for surfaces cannot be applied to multi-atom thick 2D TMDs due to the presence of interatomic bonds across the atomic surfaces. The crystal elastic model aims to solve this problem by projecting all interatomic bonds onto the mid-surface to track their deformations. The actual deformed bonds will, therefore, be computed using the deformations of the mid-surface. Additionally, a technique will be derived to incorporate the effects of curvature and stretching of TMDs on their interactions with substrates. The model will be exercised to generate insights into the mechanical instabilities and the role of substrate interactions on them. The coarse-grained model will overcome the computational bottleneck of molecular dynamics models to simulate TMDs samples comprising billions of atoms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.