溶液中的不对称离子与活性布朗粒子相似
Asymmetric Ions in Solution are Similar to Active Brownian Particles
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中文总结 AI 辅助
该研究通过分子动力学模拟发现，电荷偏移超临界值$d^*$的不对称电解质离子体坐标系会出现非零力，其扩散常数下降约400倍，且扩散常数的不同计算途径不再等价。
中文摘要 AI 辅助
对电荷相对于离子几何中心偏移距离$d$的电解质离子进行的分子动力学模拟表明，当偏移距离超过临界值$d^*$时，离子体坐标系内无法建立力学平衡。由于水分子无法通过局部密度增加来补偿静电拉力，这种受阻会导致向非零体坐标系力的急剧转变。具有不对称电荷的溶液离子会受到净体坐标系力，类似于活性物质布朗粒子的自驱动运动。此时仍保持热平衡和实验室坐标系下的零力，但当电荷位移超过阈值$d^*$时，扩散常数显著下降（约400倍）。扩散常数的不同计算途径不再等价，且由均方位移得到的扩散常数远高于由速度和力的关联函数得到的结果。
英文摘要
Molecular dynamics simulations of electrolyte ions with charge shifted by the distance $d$ from the ion geometrical center have shown that mechanical equilibrium in the ion's body frame is not established beyond a critical shift distance $d^*$. A sharp crossover to a non-zero body-frame force occurs due to frustration of water molecules failing to compensate the electrostatic pull with a local density augmentation. A solution ion with asymmetric charge experiences a net body-frame force similar to self-propelled motion of active-matter Brownian particles. Thermal equilibrium and zero laboratory-frame force are still maintained, but the diffusion constant drops significantly ($\sim 400$ times) when the charge displacement crosses the threshold value $d^*$. Alternative routes to the diffusion constant become inequivalent and the diffusion constant from the mean-squared displacement is much higher than those from velocity and force correlation functions.
