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

在行星形成的早期阶段，较小的尘埃颗粒粘在一起形成较大的颗粒。如果粒子的大小小于1公里，这些粒子表面的力被称为范德华力，被认为是导致粒子粘连在一起的原因。然而，其他力量可能会导致较小颗粒的反弹或分裂。典型的范德华力不足以阻止这些粒子分裂。研究人员将研究粒子结合在一起的可能性取决于颗粒之间的化学力，而不是范德华力，因为化学力比范德华力更强。研究人员将模拟将颗粒粘在一起的化学力和撕裂颗粒的物理力之间的相互作用，以一种代表我们现在理解的早期太阳系形成的方式。这个项目服务于国家利益，因为它促进了我们对太阳系早期建造过程的了解。调查人员将努力让桥计划的学生参与这项研究项目，作为UCF物理系作为APS桥计划站点参与的一部分，还将包括K-12和大学水平的研究成果。目前关于原行星盘中行星形成的大多数假设是基于微小的尘埃颗粒积累成宏观尘埃聚集体。在行星形成的不同阶段已经确定了几个障碍，这些障碍可能导致颗粒反弹或碎裂，而不是增加粘连和随后的颗粒增长。在直径小于1公里的范围内，地表力被认为是造成吸积的原因。这些力通常被建模为范德华力。然而，实验结果表明，范德华力的典型强度不足以防止碰撞过程中的碎裂。因此，行星形成初期的机制仍然知之甚少。研究人员在这里描述了一项计划，以证明原行星盘中粒子之间的作用力可能在多大程度上取决于矿物颗粒的化学状态。其目标是模拟化学环境中的颗粒相互作用和碰撞，以反映在行星形成的初始阶段对早期太阳系的了解。初步结果表明，颗粒表面的化学状态起着非常重要的作用，通常的弱范德华力假设往往是无效的，特别是在表面没有钝化的情况下。原子尺度的模拟结果将被用来开发粗粒度的模拟模型，这些模型可以用来理解较大聚集体之间的碰撞。作为UCF物理系作为APS桥梁项目现场参与的一部分，调查人员将努力指导几名有可能让他们参与这一研究项目的桥梁项目的学生。它们还将包括K-12和大学水平课程的研究成果。

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.