Model Medium with the Thermal and Transport Properties of Liquid Water
- PDF / 549,822 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 91 Downloads / 136 Views
OSPECTROMETRIC METHODS IN SCIENCES OF LIFE
Model Medium with the Thermal and Transport Properties of Liquid Water A. A. Vasina and A. A. Volkova,* aProkhorov
General Physics Institute, Russian Academy of Sciences, Moscow, 119991 Russia *e-mail: [email protected]
Received December 15, 2019; revised December 15, 2019; accepted February 17, 2020
Abstract—A model of a Frenkel gas–solid system that consists of H2O molecules and H3O+ and OH– ions and has the same density and particle concentration as liquid water has been considered. Particles execute thermal vibrational–diffusion motion, in the course of which they collide, exchange protons, and interconvert. Under the assumption that the medium persists owing to ion–dipole forces, it has been shown that enthalpy of vaporization H, heat capacity C, and the transport parameters of the medium (self-diffusion coefficient D, viscosity η, and thermal conductivity θ) are close to reference values for liquid water throughout the temperature interval of its existence (250–600 K). DOI: 10.1134/S1063784220090285
INTRODUCTION Although the properties of liquid water have long been a subject of intense research, they have not yet been completely understood and are considered anomalous. This problem was touched upon in the subject collection titled Water—The Most Anomalous Liquid [1] issued in 2016. To gain a deeper insight into this problem, straightforward physical models are necessary: “[f]inding simple water models reproducing as many properties as possible constitutes an important subject of research” [2]. In our research [3, 4], we drew our focus toward Frenkel’s idea of gas–solid vibrational–diffusion motion of molecules in fluids [5]. Based on published data [6], we arrived at the conclusion that the properties of water depend in equal measure on particles of three sorts: H2O molecules, H3O+ ions, and OH– ions, which execute free thermal motion, collide, exchange protons, and interconvert. As a result of collisional proton exchange, positive and negative ions execute supermolecular Brownian motion in the medium. The set of charges has its own degree of freedom of motion. The model contradicts the popular notion that water is an ensemble of inseparable H2O molecules bonded through a dense network of hydrogen bonds [7]. However, it is self-consistent and deserves checking. Below, we analyze the thermal and transport properties of the given medium and find them to be close to those of real liquid water.
1. ION–MOLECULAR MODEL OF THE MEDIUM Consider the medium depicted in Fig. 1 with geometrical parameters corresponding to liquid water: diameter d of molecules (circles in Fig. 1) is 2.8 Å, and intermolecular spacing δ is four times smaller, 0.7 Å [6]. The medium represents a dense gas of particles, which are oxygen atoms with protons randomly distributed over them. Particles with two protons are neutral water molecules (H2O), and those with one or three protons are OH– ions or H3O+ ions, respectively. Thermal collisions change the number of protons in the particles: pos
Data Loading...
