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arXiv 1004.3091cond-mat.softcond-mat.mtrl-scicond-mat.stat-mech
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水和类水液体的结构、熵与扩散系数的关系

Relationship between Structure, Entropy and Diffusivity in Water and Water-like Liquids

Manish Agarwal, Murari Singh, Ruchi Sharma, Mohammad Parvez Alam, Charusita Chakravarty

摘要:

异常行为的过剩熵($S_e$)和相关的缩放关系与扩散率进行了比较,在液体中有非常不同的基本相互作用,但类似的水状异常:水(SPC/E和TIP 3 P模型),四面体离子熔体(SiO $_2$和BeF $_2$)和流体与核心软化,两个规模斜坡(2SRP)的相互作用。我们证明了在两个水模型中存在的过剩熵异常。使用长度和能量尺度适当的异常行为的发病,密度范围的过剩熵异常被证明是在水中比在离子熔体或2SRP流体窄得多。当约化扩散系数($D^*$)符合超额熵标度关系时,所有系统的$D^* =A\exp (αS_e)$(Y。Rosenfeld,Phys.Rev.A { \bf 1977},{ \it 15},2545),指数标度参数$α$在水的情况下显示出小的等排依赖性。取代$S_e$对相关为基础的近似加重isochore-dependence的扩散率缩放。具有类似的扩散率标度参数的等值线示出具有相应的熵贡献的温度依赖性。在所有四面体液体中,扩散系数、超额熵和超额熵的对关联近似之间的关系是非常相似的。

英文摘要:

Anomalous behaviour of the excess entropy ($S_e$) and the associated scaling relationship with diffusivity are compared in liquids with very different underlying interactions but similar water-like anomalies: water (SPC/E and TIP3P models), tetrahedral ionic melts (SiO$_2$ and BeF$_2$) and a fluid with core-softened, two-scale ramp (2SRP) interactions. We demonstrate the presence of an excess entropy anomaly in the two water models. Using length and energy scales appropriate for onset of anomalous behaviour, the density range of the excess entropy anomaly is shown to be much narrower in water than in ionic melts or the 2SRP fluid. While the reduced diffusivities ($D^*$) conform to the excess entropy scaling relation, $D^* =A\exp (αS_e)$ for all the systems (Y. Rosenfeld, Phys. Rev. A {\bf 1977}, {\it 15}, 2545), the exponential scaling parameter, $α$, shows a small isochore-dependence in the case of water. Replacing $S_e$ by pair correlation-based approximants accentuates the isochore-dependence of the diffusivity scaling. Isochores with similar diffusivity scaling parameters are shown to have the temperature dependence of the corresponding entropic contribution. The relationship between diffusivity, excess entropy and pair correlation approximants to the excess entropy are very similar in all the tetrahedral liquids.

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