The volume filling degree (VFD) is a universal property of materials whose influence is often overlooked in the assessment of their property and performance. The present work exemplifies its significance by evaluating its influence on the thermal explosion of a typical 1,3,5-trinitro-1,3,5-triazinane (RDX) energetic material (EM) and the related underlying mechanism, with experimental measurements of the critical temperature for an explosion delay of 5 ​s (T_5s), and reactive molecular dynamics (MD) simulations. Three samples with different VFDs are accounted for in the T_5s measurements, whereas seven RDX-containing models are established for our MD simulations, considering two kinds of surfaces, four VFDs of 1, 0.5, 0.1, and 0.05, and three heating styles. The experimental measurements show that a higher VFD leads to a lower T_5s, or readier thermal decay. The origin of the VFD influence on T_5s is that a smaller VFD favors dissociation reactions such as the NO₂ partition, and disfavors the combination ones such as NO₂ consumption in rapid complete decay to obtain final stable products and enhance heat release. Particularly, the reduced VFD increases the energy required to complete decay, lowers the decay rate and heat release, and results in reduced temperature, pressure elevation and explosion power, in agreement with the experimental observation that a higher VFD causes a lower T_5s. Moreover, the origin of the VFD influence is principally from the pressure effect. Therefore, the VFD is crucial in the thermal decomposition of EMs because various VFDs can cause a significant difference in power. Moreover, the difference in the surface effect on the thermal decay of RDX between the (021) and (210) faces is clearly discriminated under adiabatic heating, because more activated molecules are found around the (021) face owing to the higher internal energy. In summary, the influence of VFD is significant when dealing with issues related to the surfaces of EMs.

体积填充度（VFD）是材料的通用属性，其影响通常在评估其性能和性能时被忽略。本工作通过评估其对典型的1,3,5-三硝基-1,3,5-三嗪烷（RDX）含能材料（EM）的热爆炸的影响及其相关的潜在机理，并通过实验测量来证明其重要性。爆炸延迟5 s（T _5s）的临界温度和反应分子动力学（MD）模拟。T _5s占了三个具有不同VFD的样本测量，而针对我们的MD模拟，则建立了七个包含RDX的模型，其中考虑了两种表面，四种分别为1、0.5、0.1和0.05的VFD，以及三种加热方式。实验测量结果表明，较高的VFD导致较低的T _5s或更容易的热衰减。VFD对T _5s产生影响的原因是较小的VFD有利于离解反应（例如NO ₂分配），而不利于组合反应（例如NO _2）。以快速完全衰变的方式消耗，以获得最终的稳定产物并增强热量释放。特别是，降低的VFD增加了完成衰变所需的能量，降低了衰变速率和热量释放，并导致温度，压力升高和爆炸功率降低，这与实验观察表明，更高的VFD导致更低的T _5s。此外，VFD影响的根源主要来自压力效应。因此，VFD在EM的热分解中至关重要，因为各种VFD可能会导致功率上的显着差异。而且，在绝热加热下，（021）和（210）面之间对RDX的热衰变的表面效应的差异明显地被区别开了，因为由于较高的内能，在（021）面周围发现了更多的活化分子。总之，在处理与EM表面有关的问题时，VFD的影响很大。