Siloxane working fluid has good environmental performance and thermodynamic performance, widely used in high temperature heat source ORC system. During the filling process of working fluid and operation in ORC system operation, air may leak into the system. The reaction of siloxane working fluid with oxygen in high temperature environment will produce abrasive silica, which will cause serious damage to the system. The oxidative decomposition mechanism of hexamethyldisiloxane (MM) was analyzed by density functional theory (DFT) and ReaxFF molecular dynamic simulation. It is found that the initial reactions of MM oxidation decomposition can be divided into two categories. The first type is the thermal decomposition of MM itself. The second one is the collision reaction between MM molecule and O₂ molecule. Comparing the two kinds of chemical reaction barriers, MM is more likely to react with O₂. Pathways 2–3 involving the collision between O₂ molecule and Si atom are the optimal pathway of initial reaction kinetics, and its reaction energy barrier is 204.1 kJ/mol. It was observed from ReaxFF MD simulations that the main products of MM oxidative decomposition were CH₄, CH₂O, CO, CO₂, SiO and amorphous silica. In the process of oxidative decomposition, small free radicals such as CH₃, O, H, OH played a very important role in the oxidative decomposition of working fluids, which greatly promoted the decomposition of working fluids and the formation of main products.

硅氧烷工质具有良好的环保性能和热力学性能，广泛应用于高温热源ORC系统。在ORC系统运行中的工作液加注过程和运行过程中，空气可能会泄漏到系统中。硅氧烷工作液在高温环境下与氧气反应会产生具有磨蚀性的二氧化硅，对系统造成严重的破坏。通过密度泛函理论(DFT)和ReaxFF分子动力学模拟分析了六甲基二硅氧烷(MM)的氧化分解机理。发现MM氧化分解的初始反应可分为两类。第一类是MM本身的热分解。_{第二个是MM分子与O 2}的碰撞反应分子。比较两种化学反应能垒，MM更容易与O ₂发生反应。_{涉及O 2}分子与Si原子碰撞的途径2-3是初始反应动力学的最佳途径，其反应能垒为204.1 kJ/mol。由ReaxFF MD模拟观察到，MM氧化分解的主要产物是CH ₄、CH ₂ O、CO、CO ₂、SiO和无定形二氧化硅。_{在氧化分解过程中，CH 3} 、O、H、OH等小自由基对工质的氧化分解起着非常重要的作用，极大地促进了工质的分解和主要产物的形成。