Elder Robert M, Saylor David M
Center for Devices and Radiological Health, FDA, Silver Spring, Maryland 20903, United States.
J Phys Chem B. 2022 May 26;126(20):3768-3777. doi: 10.1021/acs.jpcb.2c00057. Epub 2022 May 18.
We demonstrate a novel application of the time-temperature superposition (TTS) principle to predict solute diffusivity in glassy polymers using atomistic molecular dynamics simulations. Our TTS approach incorporates the Debye-Waller factor ⟨⟩, a measure of solute caging, along with concepts from thermodynamic scaling methods, allowing us to balance contributions to the dynamics from temperature and ⟨⟩ using adjustable parameters. Our approach rescales the solute mean-squared displacement curves at several temperatures into a master curve that approximates the diffusive dynamics at a reference temperature, effectively extending the simulation time scale from nanoseconds to seconds and beyond. With a set of "universal" parameters, this TTS approach predicts with reasonable accuracy in a broad range of polymer/solute systems. Using TTS greatly reduces the computational cost compared to standard MD simulations. Thus, our method offers a means to rapidly and routinely provide order-of-magnitude estimates of using simulations.
我们展示了时间-温度叠加（TTS）原理的一种新应用，即使用原子分子动力学模拟来预测玻璃态聚合物中溶质的扩散系数。我们的TTS方法结合了德拜-瓦勒因子⟨⟩（一种溶质笼效应的度量）以及热力学标度方法的概念，使我们能够使用可调参数来平衡温度和⟨⟩对动力学的贡献。我们的方法将几个温度下溶质的均方位移曲线重新标度为一条主曲线，该主曲线近似于参考温度下的扩散动力学，有效地将模拟时间尺度从纳秒扩展到秒及更长时间。通过一组“通用”参数，这种TTS方法在广泛的聚合物/溶质系统中能以合理的精度进行预测。与标准分子动力学模拟相比，使用TTS大大降低了计算成本。因此，我们的方法提供了一种通过模拟快速且常规地提供数量级估计的手段。
