Improving molecular dynamics calculation of diffusivity in liquids with theoretical models

Molecular dynamics analysis of elastic properties and new phase formation during amorphous ices transformations

Unlike conventional first-order phase transitions, the kinetics of amorphous-amorphous transitions has been much less studied. The ultrasonic experiments on the transformations between low-density and high-density amorphous ice induced by pressure or heating provided the pressure and temperature dependencies of elastic moduli. In this article, we make an attempt to build a microscopic picture of these experimentally studied transformations using the molecular dynamics method with the TIP4P/Ice water model. We study carefully the dependence of the results of elastic constants calculations on the deformation rates. The system size effects are considered as well. The comparison with the experimental data enriches our understanding of the transitions observed. Our modeling gives new information about the formation mechanisms of new phase clusters during the transition between low-density and high-density amorphous ices. We analyse the applicability of the term "nucleation" for these processes.

Molecular Dynamics Simulation and Structure Changes of Polyester in Water and Non-Aqueous Solvents

Studying the changes in the microstructure of polyester (PET) in water and non-aqueous solvents is important to understand the swelling mechanism of PET, which can help to reduce water pollution during the dyeing process. This study uses molecular models of PET, water, and decamethyl-cyclopentasiloxane (D5) and employs molecular dynamics method to simulate the influence of solvents on the microstructure of PET. The results show that the glass transition temperature (T_g) of the pure PET system is close to the experimental value. The T_g of PET decreases with the addition of water and D5 solvents, and the free volume after adding D5 is higher compared to the free volume after adding water. Through molecular dynamics simulation of PET microstructure, it is found that D5 has a better SWELLING effect on PET than water.