CHARMM Force Field Calculation Of Water Cluster And Molten CsCl-KCl

Water clusters are widely used in engineering applications,which makes it increasingly necessary to understand the structure and properties of water clusters at the atomic level.Through theoretical calculation and experimental means,water clusters are studied to help researchers understand the micro-structure of water clusters,and lay a solid foundation for the establishment of water molecular system model.Thermodynamic properties and structures of alkali metal chlorides are an important part of molten salt theory.It is instructive to study the thermodynamic properties of molten salts.Under the conditions of NVT canonical ensemble and three-dimensional periodic boundary conditions,the structure and atomic/ion motion of different size water clusters(H2O)n and molten CsCl-KCl with different proportions at different temperatures were calculated by using the NAMD method based on the CHARMM force field.At the same water molecule number,the peak value of the distribution function of oxygen atom-oxygen atom decreases with the increase of temperature;the peak value of the distribution function of oxygen atom-hydrogen atom and two hydrogen atoms is not affected by temperature;at the same temperature,the distribution function of oxygen atom-oxygen atom,oxygen atom-hydrogen atom and two hydrogen atoms decreases with the increase of n,and at n=128.At the same time,it gradually increases.Mean azimuth shift increases with the increase of temperature;form factor increases with the increase of water molecule number,and the larger the water molecule number,the smaller the influence of temperature on the shape factor of the system;the rotational partition function increases with the increase of temperature and water molecule number,but the effect of temperature on it is small;the rotational partition function of translational partition function increases with the increase of temperature and water molecule number.The free energy decreases with the increase of water molecule number and is inversely proportional to temperature.At the same temperature,the distribution function of molten CsCl-KCl decreases with the increase of temperature;at the same temperature,the peak value of Cs+1-Cs+1 pair distribution function increases with the increase of proportion,while K+1-K+1 pair distribution function fluctuates with the change of temperature,and the peak value of other ion pairs decreases with the change of proportion.The coordination number of Cs+1-Cl-1 and K+1-K+1 decreases with the increase of temperature;when the ratio of CsCl-KCl is 1:16 and 1300K,the maximum coordination number of Cs+1-Cs+1 is 11.5,while when the ratio of CsCl-KCl is 1:16,the coordination number of Cs+1-Cl-1 decreases with the increase of temperature;when the ratio of CsCl-KCl is 1:16,the coordination number of Cs+1-Cl-1 increases with the increase of temperature,but under other ratios,the concentration of CsCl has no obvious shadow.The coordination number of K+1-Cl-1 is not affected by the concentration of CsCl.When the ratio of CsCl-KCl is 1:16 and 1:8,the average azimuth shift of ions increases with the increase of temperature;when the ratio of CsCl-KCl is 1:4,1:2 and 1:1,the average azimuth shift of ions increases with the increase of temperature,but when the temperature continues to rise from 1300K,the average azimuth shift of ions decreases with the increase of temperature.