Fractional Stokes-Einstein relation in TIP5P water at high temperatures

• 来源期刊: 中国物理B（英文版）
• 关键词: Stokes-Einstein relation TIP5P water molecular dynamics hydration shells
• 年，卷（期）: 2018,（6）
• 页码范围: 305-312
• 页数: 8页
• 语种: 英文
• DOI: 10.1088/1674-1056/27/6/066101

摘要

Fractional Stokes-Einstein relation described by D ～ (τ/T)ξ is observed in supercooled water,where D is the diffusion constant,τ the structural relaxation time,T the temperature,and the exponent ξ ~-1.In this work,the StokesEinstein relation in TIP5P water is examined at high temperatures within 400 K-800 K.Our results indicate that the fractional Stokes-Einstein relation is explicitly existent in TIP5P water at high temperatures,demonstrated by the two usually adopted variants of the Stokes-Einstein relation,D ～ τ-1and D ～ T/τ,as well as by D ～ T/rη,where ηis the shear viscosity.Both D ～ τ-1 and D ～ T/τ are crossed at temperature Tx =510 K.The D ～ τ-1 is in a fractional form as D ～ τξ with ξ =-2.09 for T ≤ Tx and otherwise ξ =-1.25.The D ～ T/τ is valid with ξ =-1.01 for T ≤ Tx but in a fractional form for T ＞ Tx.The Stokes-Einstein relation D ～ T/η is satisfied below Tx =620 K but in a fractional form above Tx.We propose that the breakdown of D ～ T/η may result from the system entering into the super critical region,the fractional forms of D ～ τ-1 and D ～ T/τ are due to the disruption of the hydration shell and the local tetrahedral structure as well as the increase of the shear viscosity.