Molecular Dynamics Simulations of Water in Confined Surfaces

The freezing and thaw cycles of water in confined media, such as the pores of soil, need to be understood as it impacts infrastructure development in cold regions experiencing the effect of large variations in temperature. In this project we use the TIP4P/2005 model of water in the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) to try and uncover some poorly understood qualities of water. The four site TIP4P/2005 model was chosen over other water models, and even over other four site models, since it gave the most accurate results for density over other models for hexagonal ice. This model includes sites for two hydrogen atoms, one oxygen atom, and a virtual "m" atom between the two hydrogen atoms. Previous literature shows that when liquid-ice boundaries are coexisting with solid surfaces there is a solidification effect on the water molecules even with minimal or no change in temperature or pressure. The Vashishta potential was used to simulate the interactions between the SiO2 wall atoms, and an NPT ensemble was decided upon for our calculations in order to maintain consistency with the literature. For initial simulations we used walls made of an alpha-quartz silica lattice and compared it to walls of amorphous silica glass. Our results will enable us to understand the fundamental principles governing ice formation in confined systems.