具有移位偶极子的Stockmayer流体：整体行为
Stockmayer Fluid with a Shifted Dipole: Bulk Behavior
AI总结：
研究发现偶极子位移影响液体结构和介电响应，揭示了几何摩擦对相行为的调控作用。
摘要：
将点偶极子从Stockmayer粒子中心移位是一种简单的几何修改，此前已有探索，但其对液体结构、介电响应和相行为的影响仍不完全理解。本文结合分子动力学模拟与解析理论，提供了一种统一的物理解释，说明偶极子位移如何重塑微观相关性并传播到宏观热力学性质。我们证明，偶极子位移破坏了局部静电场的前后对称性，导致径向堆积仅有适度变化，但在第一溶剂壳内产生强烈的角结构变化。靠近偶极子头部增强的对齐性伴随尾部附近方向相关性的摩擦，导致更广的角分布和强耦合下远离轴向配置。这些结构不对称性削弱了协同有序性，尽管局部相互作用更强，但导致介电常数系统性降低。对于大位移，介电响应接近德拜极限，表明偶极子-偶极子相关性被有效抑制。相同的几何摩擦支配气-液平衡：尽管增加偶极子强度提高临界温度，但即使适度位移也会破坏强耦合下出现的高极化液态，可能抑制铁电样有序。重新参数化的COFFEE理论预测在有效域内捕捉这些趋势，突显了局部方向结构与宏观可观测量之间的直接联系。总体而言，本文表明偶极子位置，而不仅是大小，是偶极子流体中强有力的控制参数，并提供了理解静电液体中几何摩擦的清晰框架。
英文摘要：
Shifting the point dipole from the center of a Stockmayer particle is a simple geometric modification that has been explored previously, yet its implications for liquid structure, dielectric response, and phase behavior remain incompletely understood. Here, we combine molecular dynamics simulations with analytical theory to provide a unified physical interpretation of how dipole displacement reshapes microscopic correlations and propagates to macroscopic thermodynamic properties. We show that dipole shifting breaks the fore-aft symmetry of the local electrostatic field, producing only modest changes in radial packing but strong alterations in angular structure within the first solvation shell. Enhanced alignment near the dipole head is accompanied by frustrated orientational correlations near the tail, leading to broader angular distributions and a shift away from axial configurations at strong coupling. These structural asymmetries weaken cooperative ordering and result in a systematic reduction of the dielectric constant, despite locally stronger interactions. For large shifts, the dielectric response approaches the Debye limit, indicating effective suppression of dipole-dipole correlations. The same geometric frustration governs vapor-liquid equilibria: while increasing dipole strength raises the critical temperature, even modest shifts disrupt the highly polarized liquid states that emerge at strong coupling and can suppress ferroelectric-like ordering. Predictions from a reparameterized COFFEE theory capture these trends within its domain of validity, highlighting the direct connection between local orientational structure and macroscopic observables. Overall, this work demonstrates that dipole location, not only magnitude, provides a powerful control parameter in dipolar fluids and offers a clear framework for understanding geometric frustration in electrostatic liquids.
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