Clathrates, Monte Carlo simulations

An important step in understanding the local structure around a nonpolar solute in water was made by Jorgensen et al. Using Monte Carlo simulations based on an intermolecular potential, which contained Lennard-Jones and Coulomb contributions, they determined the number of water molecules in the first hydration layer (located between the first maximum and the first minimum of the radial distribution function) around a nonpolar solute in water. This number (20.3 for methane, 23 for ethane, etc.) was surprisingly large compared with the coordination numbers in cold water and ice (4.4 and 4, respectively). These results provided evidence that major changes occur in the water structure around a nonpolar solute and that the perturbed structure is similar to that of the water—methane clathrates, ... 

Demurov, A., Radhakrishnan, R., Trout, B.L., Computations of diffusivities in ice and CO2 clathrate hydrates via molecular dynamics and Monte Carlo simulations. J. Chem. Phys., 116 (2002) 702-709. 

A. Demurov, R. Radhakrishnan, and B. L. Trout,/. Chem. Phys., 116, 702 (2002). Computations of Diffusivities in Ice and CO2 Clathrate Hydrates via Molecular Dynamics and Monte Carlo Simulations. 

The next four chapters address several applications of MD to water and aqueous solutions. Floris and Tani describe tiie development of force fields for water-water and water-ion interactions in Chapter 10. Balbuena et al. analyze force fields for cation-water systems introducing new descriptions of short-range interactions. Li and Tomkinson assess the estimation of neutron scattering spectra of ice by MD and lattice dynamics simulations in Chapter 12. Tanaka in Chapter 13 discusses the stability and dynamics of ice and clathrate hydrate using Monte Carlo, MD, lattice dynamics simulations, and a statistical mechanical formulation. 

We treat, in this chapter, mainly solid composed of water molecules such as ices and clathrate hydrates, and show recent significant contribution of simulation studies to our understanding of thermodynamic stability of those crystals in conjunction with structural morphology. Simulation technique adopted here is not limited to molecular dynamics (MD) and Monte Carlo (MC) simulations[l] but does include other method such as lattice dynamics. Electronic state as well as nucleus motion can be solved by the density functional theory[2]. Here we focus, however, our attention on the ambient condition where electronic state and character of the chemical bonds of individual molecules remain intact. Thus, we restrict ourselves to the usual simulation with intermolecular interactions given a priori. 

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