Atoms-in-Molecules Molecular-dynamics Study Of Ion-water Bonding Of K~+ Solvation In Water

Water is not only a valuable natural resource, but also a necessary survival condition of human being. Water is ubiquitous and one of the most important liquids to investigate. Due to its critical role in many chemical and biological processes,a detailed understanding of the structural and dynamical properties of water is essential.The properties of water are dominated by its ability to form hydrogen bond networks. The networks are dynamic, with the strengths and numbers of hydrogen bonds associated with a particular water molecule constantly fluctuating. It is generally accepted that the distinctive properties of water can be ascribed to hydrogen bonding.The fundamental dynamical processes of the liquid is the forming and breaking of hydrogen bonds. This dynamics, however, is far from being completely understood!Besides ,Water clusters combined with a variety of metal ions plays a very important role in chemistry and biology. For example, the alkali ion-water bonding, such as K~+, plays a key role on understanding the selectivity of biological ion channels. This article we introduce ion-water bonding of K~+ solvation in Water.Now, Car-Parrinello molecular dynamics (CPMD) has become the most important ab initio molecular dynamics method based on the first principle theory. In this paper, we carried out studies of liquid water with CPMD computational methods to study the properties of liquid water.Through statistical analysis of the simulation results of liquid water and ion-water bonding of K~+ solvation in Water, we get the these data the following conclusions are:1.The nearly linear relationship between hydrogen bond strength at the CCSD(T)/Aug-cc-pVTZ level and the electron density at the bond critical point in the Atoms-In-Molecules theory provides a practical means of calculating the hydrogen bond strength in liquid water.2.A statistical analysis of the hydrogen bonds obtained from Car?Parrinello molecular dynamics simulations shows that the strengths of hydrogen bonds in liquid water conform to a Gaussian distribution.3. Considering supercooled (250 K) water to have a fully coordinated (ice-like) local tetrahedral configuration, we show that the local structure of liquid water is partly distorted tetrahedral in normal liquid water and even in superheated water.4. The K~+-oxygen radial distribution function indicated that the perturbation of K~+ on the water structure is strong in the first hydration shells, while it is mild outside of this region in normal liquid.5. The K~+-oxygen radial distribution function indicated that the perturbation of K~+ on the water structure is strong in the first hydration shells, while it is mild outside of this region in normal liquid.6. According to our natural geometric criterion for the coordinated oxygen atom, the average coordination number of K~+ is 6.24 and 6.53 at 300K and 450K, respectively, which agrees with the experimental value (6.1). This geometric criterion can also be used to define strong, moderate and weak hydrogen bonds in liquid.Through the research and analysis of the system of water molecules we got some quantitative results. Gave us more profounding understands of the microscopic nature of the liquid water.