Developing machine-learned potentials to simultaneously capture the dynamics of excess protons and hydroxide ions in classical and path integral simulations
Austin O. Atsango, Tobias Morawietz, Ondrej Marsalek, Thomas E. Markland
The transport of excess protons and hydroxide ions in water underlies numerous important chemical and biological processes. Accurately simulating the associated transport mechanisms ideally requires utilizing ab initio molecular dynamics simulations to model the bond breaking and formation involved in proton transfer and path-integral simulations to model the nuclear quantum effects relevant to light hydrogen atoms. These requirements result in a prohibitive computational cost, especially at the time and length scales needed to converge proton transport properties. Here, we present machine-learned potentials (MLPs) that can model both excess protons and hydroxide ions at the generalized gradient approximation and hybrid density functional theory levels of accuracy and use them to perform multiple nanoseconds of both classical and path-integral proton defect simulations at a fraction of the cost of the corresponding ab initio simulations. We show that the MLPs are able to reproduce ab initio trends and converge properties such as the diffusion coefficients of both excess protons and hydroxide ions. We use our multi-nanosecond simulations, which allow us to monitor large numbers of proton transfer events, to analyze the role of hypercoordination in the transport mechanism of the hydroxide ion and provide further evidence for the asymmetry in diffusion between excess protons and hydroxide ions.
Ab initio studies of ionization potentials of hydrated hydroxide and hydronium
用多体方法计算了氢氧化物和水合氢离子的电离势分布，电子激发构型由{ \it ab initio}分子动力学产生。实验结果得到了很好的再现，并与分子激发态密切相关。在稳定构型中，电离势主要受第一溶剂化层内水分子的扰动。另一方面，在质子转移过程中，电子激发在质子接收复合物和质子供给复合物上都是离域的，这使得两种水合离子的激发能发生移动，光谱变宽。
Revealing Hydroxide Ion Transport Mechanisms in Commercial Anion-Exchange Membranes at Nano-Scale from Machine-learned Interatomic Potential Simulations
Technische Universität Ilmenau（伊尔梅瑙工业大学）；Fraunhofer-Institut für Keramische Technologien und Systeme IKTS（弗劳恩霍夫陶瓷技术与系统研究所）
Plasma-activation of tap water using DBD for agronomy applications: Identification and quantification of long lifetime chemical species and production/consumption mechanisms
Magnesium Contact Ions Stabilize the Tertiary Structure of Transfer RNA: Electrostatics Mapped by Two-Dimensional Infrared Spectra and Theoretical Simulations
