The Garrod group uses a selection of computational models and tools to study and simulate the chemistry of the interstellar medium, star-forming regions, solar-system bodies, and low-temperature laboratory ices. The majority of the codes we use are developed within the group. Models we have developed include the three-phase (gas/grain-surface/ice) chemical kinetics code MAGICKAL, and the off-lattice microscopic Monte Carlo kinetics model MIMICK, which is used to simulate both interstellar and laboratory ice chemistry.
More information on Garrod Group research can be found under individual subheadings.
The image below shows simulated laboratory water-ice structure obtained using the Garrod group's MIMICK model. Water molecules are deposited from the gas-phase at room temperature onto a cold (85 K) surface. The model simulates the deposition process, as well as the chemical kinetics of surface diffusion, which determines the ultimate structure and porosity of the ice.
The image below shows cross-sections through interstellar dust-grain ices, as simulated using MIMICK, formed at temperatures 8 - 12 K. The ice formation takes place on the surface of an approximately spherical dust grain (not shown in images) of radius ~100 Å. The ice is composed mainly of water, but also contains significant quantities of CO, CO2, CH4, NH3, and various other related species. Production of the ices occurs through the accretion of atoms and simple molecules from the gas phase, followed by diffusion-mediated chemistry, which at these low temperatures is dominated by the addition of H atoms to surface atoms and molecules. The degree of porosity in the ice is dependent on both the temperature (increasing from left to right in the figure) and the gas density at which deposition occurs. The abundance of gas-phase atomic hydrogen decreases over time, resulting in less hydrogen-rich ice in the outer layers.
