Supercritical fluids are substances at a temperature and pressure above their critical point. They play important roles in industrial fields, especially in the field of extraction, since they change their physicochemical properties greatly with a slight temperature and pressure change. Previous experimental and computational studies have clarified that the local densities of supercritical fluids show fluctuations. This means that there is complex dynamics governed by the balance among various intermolecular potentials and kinetic energy in the supercritical phase. For understanding physicochemical properties of supercritical fluids, it is mandatory to model the condensed phase with enough large number of molecules for describing the density fluctuation. Since the intermolecular interaction in supercritical phase is not trivial due to their high pressure, it should be better to model them without using any pre-optimized parameters. However, such a large-scale ab initio molecular dynamics (AIMD) simulation for modeling condensed phase is not often realistic due to their high computational costs. In this presentation, we will show an alternative method for supercritical fluids simulation, effective fragment potential-molecular dynamics (EFP2-MD), which balance the accuracy and computational costs of ab initio MD simulations. EFP2 is an ab initio polarizable intermolecular potential, where electrostatic, exchange repulsion, polarization and dispersion interactions are evaluated without using any pre-optimized parameter. In the EFP2, each intermolecular interaction component is described with a compact set of multipoles and localized orbitals defined by an ab initio molecular orbital calculation with rigid-rotor approximation. In this poster session, we will discuss the possibility of describing density fluctuation of supercritical fluids, including rare gases, CO2, etc., with EFP2-MD simulations.

Challenge for predicting physicochemical properties of supercritical fluids and compressed liquids: An ab initio Effective Fragment Potential ver.2 – MD simulation study

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.