Zielkiewicz Jan
Department of Chemistry, Gdańsk University of Technology, Gdańsk, Poland.
J Phys Chem B. 2008 Jul 3;112(26):7810-5. doi: 10.1021/jp7103837. Epub 2008 Jun 6.
Entropies of simple point charge (SPC) water were calculated over the temperature range 278-363 K using the two-particle correlation function approximation. Then, the total two-particle contribution to the entropy of the system was divided into three parts, which we call translational, configurational, and orientational. The configurational term describes the contribution to entropy, which originates from spatial distribution of surrounding water molecules (treated as points, represented by the center of mass) around the central one. It has been shown that this term can serve as the metric of the overall orientational ordering in liquid water. Analyzing each of these three terms as a function of intermolecular distance, r, we also find a rational definition of the hydration shell around the water molecule; the estimated radii of the first and second hydration shells are 0.35 nm and 0.58 nm, respectively. We find, moreover, that the first hydration shell around the water molecule participates roughly in 70% of the total orientational entropy of water, and this rate is roughly temperature independent.
利用双粒子关联函数近似计算了简单点电荷（SPC）水在278 - 363 K温度范围内的熵。然后，将系统熵的总双粒子贡献分为三部分，我们称之为平动、构型和取向部分。构型项描述了对熵的贡献，它源于中心水分子周围周围水分子（视为点，由质心表示）的空间分布。已经表明，该术语可以作为液态水中整体取向有序性的度量。将这三个项中的每一项作为分子间距离r的函数进行分析，我们还找到了水分子周围水化层的合理定义；第一和第二水化层的估计半径分别为0.35 nm和0.58 nm。此外，我们发现水分子周围的第一水化层大约参与了水的总取向熵的70%，并且该比率大致与温度无关。
