Chemical and Dynamical Forces in Building Large Particles in the Disks Around Young Stars

在年轻恒星周围的盘中形成大粒子的化学力和动力

• 批准号: 1616511
• 负责人: Patrick Schelling
• 金额: $ 38.29万
• 依托单位: The University of Central Florida Board of Trustees
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-15 至 2021-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1616511&HistoricalAwards=false
• 关键词: Chemical; Dynamical; Forces; Building; Large

During the early stages of planet formation, small dust particles stick together to form larger particles. If the particles are smaller than 1 km in size, forces on the surfaces of these particles, called van der Waals forces, are thought to cause the particles to stick together. Other forces, however, can cause bouncing or breaking apart of the smaller particles. The typical van der Waals force is not strong enough to stop these particles from breaking apart. The investigators will study the possibility that particles joining together depend on chemical forces between the grains, not the van der Waals forces, as the chemical forces are stronger than van der Waals forces. The investigators will model the interaction between chemical forces sticking grains together and physical forces breaking grains apart, in a way that represents the early Solar System formation as we now understand it. This project serves the national interest as it advances our knowledge of the early building processes of the Solar System. The investigators will work to include Bridge Program students in this research project, as part of the UCF Physics Department's participation as an APS Bridge Program site, and will also include research results in K - 12 and college-level classes.Most current hypotheses for the formation of planets in protoplanetary disks are based on the accretion of small dust grains into macroscopic dust aggregates. Several barriers have been identified at different stages of planet formation that could lead to bouncing or fragmentation of particles instead of increased sticking together and subsequent growth of particles. At sizes less than ~1km in diameter, surface forces are thought to be responsible for accretion. These forces are typically modeled as van der Waals forces. Experimental results, however, indicate that the typical strength of the van der Waals force is not sufficient to prevent fragmentation during collisions. Consequently, the mechanisms for the initial stages of planet formation remain poorly understood. The investigators describe here a plan to demonstrate how much the forces between particles in protoplanetary disks might depend on the chemical state of the mineral grains. The objective is to model grain interactions and collisions in a chemical environment that is intended to reflect what is known about the early Solar System during the initial stages of planet formation. Preliminary results indicate that the chemical state of grain surfaces plays an extremely important role, and the usual assumption of weak van der Waals forces is often invalid especially when surfaces are not passivated. Atomic-scale simulation results will be used to develop coarse-grained simulation models that can be used to understand collisions between larger aggregates. As part of the UCF Physics Department's participation as an APS Bridge Program site, the investigators will work to mentor several Bridge Program students with the potential to involve them in this research project. They will also include research results in K - 12 and college-level classes.

在行星形成的早期阶段，小的尘埃颗粒粘在一起形成较大的颗粒。如果粒子的尺寸小于1公里，则这些粒子表面上的力，称为货车德瓦尔斯力，被认为是导致粒子粘在一起的原因。然而，其他的力可以导致较小颗粒的反弹或破碎。典型的货车范德华力不足以阻止这些粒子分裂。研究人员将研究颗粒结合在一起取决于颗粒之间的化学力而不是货车德瓦尔斯力的可能性，因为化学力比货车德瓦尔斯力更强。研究人员将模拟将颗粒粘在一起的化学力和将颗粒分开的物理力之间的相互作用，以代表我们现在所理解的早期太阳系形成的方式。这个项目为国家利益服务，因为它促进了我们对太阳系早期建造过程的了解。研究人员将努力将桥梁计划的学生纳入这项研究项目，作为UCF物理系参与APS桥梁计划网站的一部分，还将包括K - 12和大学水平课程的研究成果。目前大多数关于原行星盘中行星形成的假设都是基于小尘埃颗粒吸积成宏观尘埃聚集体。在行星形成的不同阶段已经确定了几个障碍，这些障碍可能导致粒子的反弹或破碎，而不是增加粘在一起和随后的粒子增长。在直径小于1公里的尺度上，表面力被认为是造成吸积的原因。这些力通常被建模为货车范德华力。然而，实验结果表明，货车范德华力的典型强度不足以防止碰撞过程中的碎裂。因此，行星形成的初始阶段的机制仍然知之甚少。研究人员在这里描述了一个计划，以证明原行星盘中粒子之间的作用力可能取决于矿物颗粒的化学状态。其目的是模拟颗粒在化学环境中的相互作用和碰撞，以反映行星形成初期太阳系的已知情况。初步结果表明，晶粒表面的化学状态起着极其重要的作用，通常假设的弱货车范德华力往往是无效的，特别是当表面不钝化。原子尺度的模拟结果将用于开发粗粒度的模拟模型，可用于了解较大聚集体之间的碰撞。作为UCF物理系作为APS桥梁项目网站参与的一部分，研究人员将努力指导几个桥梁项目的学生，使他们有可能参与到这个研究项目中。它们还将包括K - 12和大学水平课程的研究成果。