Computational Modeling of Chemical Reactions in Ultrasound Baths

超声波浴在许多化学实验室中用于粉碎和混合物质。此外，声化学，即通过超声波引发化学反应，是化学的一个有趣的分支，越来越受欢迎。尽管已知超声浴中的分子暴露于机械剪切力、几千开尔文的温度和超过一千个大气压的压力，但是直到今天还不存在用于模拟超声浴中的分子的计算方法。因此，合理的设计声化学反应是不可能的，使这些过程的规划和优化复杂化。在这个项目中，开发了一种用于模拟超声浴中分子的计算方法。最初，重点在于聚合物，因为超声波浴是一种成熟的方法，用于聚合物链的展开和断裂，并且已经描述了大量的实验观察结果，新方法可以作为基准。在项目的后期阶段，也将研究有机声化学中的反应。对于超声浴中的分子描述，使用分子动力学（MD）和Born-Oppenheimer分子动力学（BOMD）模拟。除了对在空化气泡破裂时暴露于冲击波的聚合物链进行明确的经典模拟外，在项目过程中，还将应用既定的方法来模拟外力以及高温和高压下的分子。例如，在BOMD模拟中，机械力将通过EFEI（External Force is Explained Included）方法施加，压力将通过X-HCFF（eXtended Hydrostatic Compression Force Field）方法施加。通过这些因素的适当组合以及分子在时间上的传播，可以逼真地模拟超声浴中的化学过程。该项目的目的是正确再现暴露于超声波的聚合物链中的材料失效点，以及准确预测有机声化学中的反应产物。

Ultrasound baths are used in many chemical laboratories for shredding and mixing of substances. In addition, sonochemistry, i.e. the initiation of chemical reactions by ultrasound, is an intriguing branch of chemistry that enjoys increasing popularity. Although it is known that molecules in ultrasound baths are exposed to mechanical shear forces, temperatures of several thousand Kelvin and pressures of more than a thousand atmospheres, no computational method for the simulation of molecules in ultrasound baths exists until the present day. Hence, a rational design of sonochemical reactions is impossible, complicating the planning and optimization of these processes.In this project, a computational method for the simulation of molecules in ultrasound baths is developed. Initially, the focus lies on polymers, since ultrasound baths are a well-established method for the unfolding and rupture of polymer strands and a plethora of experimental observations against which the new method can be benchmarked have been described. In the later stages of the project, reactions in organic sonochemistry will be investigated as well.For the description of molecules in ultrasound baths, Molecular Dynamics (MD) and Born-Oppenheimer Molecular Dynamics (BOMD) simulations are used. In addition to the explicit classical simulation of a polymer strand that is exposed to a shock wave upon collapse of a cavitational bubble, during the course of the project, established methods for the simulation of molecules under external forces as well as high temperatures and pressures will be applied. In the BOMD simulations, for example, mechanical forces will be applied via the EFEI (External Force is Explicitly Included) approach and pressures via the X-HCFF (eXtended Hydrostatic Compression Force Field) method. Through an appropriate combination of these factors as well as the propagation of the molecules in time, the chemical processes in ultrasound baths can be modeled realistically. The aim of this project is the correct reproduction of the points of material failure in polymer strands that are exposed to ultrasound as well as the accurate prediction of the reaction products in organic sonochemistry.