Prof. Martin Dove Project Abstracts

BSc Project Abstracts

Disordered crystalline materials; what can we learn from novel diffraction methods
We have a strong interest in understanding the fluctuations in the positions of atoms within crystal structures that appear to have a lot of structural disorder. Examples include materials in which some atoms diffuse at a fast rate through the background crystal structure (so called fast-ion conductors that are used as electrolytes in solid-state batteries), and molecular materials where the orientations are disordered and tumbling when the positions are ordered on a lattice, or liquid crystals where the molecules have well-defined orientations but disordered positions. In this project we will combine a diffraction-based method (using either neutrons or x-rays) with subsequent date-oriented computer simulation to study one specific example (this will be chosen by the student). You will be using state-of-the-art experimental methods (which may include a visit to the UK neutron scattering facility, and the use of an x-ray facility at Queen Mary) together with novel analysis methods developed in part by Queen Mary scientists. The end result will be a new insight into the local structure and fluctuations of a material, which will certainly be publishable in the scientific literature.

Capture of carbon dioxide using porous crystalline materials
One critically important environmental problem for modern societies is that of controlling the mount of CO2 we put into the environment. One solution is to capture CO2 at the industrial sources. Current methods are expensive, and there is a lot of interest in looking for new materials for this task. One approach is to use porous crystalline materials, with a lot of interest in hybrid metal-organic materials that form crystal structures that contain large pores and channels. The project is to use computer simulations to understand the mechanisms of CO2 absorption in materials. The approach is to use a technique called molecular dynamics, which is a form of virtual reality at atomic length and time scales. The project will involve setting up a simulation of passing gases across a sample and observing the way that the material soaks carbon dioxide out of the gas stream. The project will require simulations over a range of temperatures and for a range of gas compositions, and will focus on both the capture of CO2 and it subsequent release. The end result will be an evaluation of a specific type of material for capture of CO2, which can be published as a scientific paper.

Anomalous properties of framework materials
One very curious property of some materials is that they shrink when heated, contrary to the normal case of expanding. We have ideas about why this might be so, and here I am offering two projects, both of which are based on computer simulations. Both will lead to results we will publish as scientific papers.

1. One family of materials that displays negative thermal expansion is zeolites, which have chemical formula SiO2 and in which the structure forms SiO4 tetrahedra that are linked at corners to form infinite connected networks. The existence of negative thermal expansion is associated with the ability of the network to flex with low energy cost. The project will involve simulations of the dynamics, using lattice dynamics calculations and molecular dynamics (a form of virtual reality). The aim will be to identify negative thermal expansion in a group of zeolites (those with hexagonal crystal structure) and to then assess it against models of network flexibility.

2. A second family, represented by the formula ZrP2O7, shows negative or positive thermal expansion depending on the detailed chemical composition. The crystal structure consists of ZrO6 octahedra and PO4 tetrahedra linked at corners to form an infinite connected network. This network, however, is not flexible, and the origin of negative thermal expansion must lie in the ability of either the octahedra or tetrahedra to distort. The project will use ab initio lattice dynamics calculations (calculations based on a form of quantum mechanics) to evaluate the phonons, and we will then match the associated atomic motions with flexibility models. The aim will be to identify the mechanism of negative thermal expansion, and to understand why some members of this family of structures show negative thermal expansion whereas other members don’t.

MSci Review Project Abstracts

Simulation methods to study capture of carbon dioxide using porous crystalline materials
One critically important environmental problem for modern societies is that of controlling the mount of CO2 we put into the environment. One solution is to capture CO2 at the industrial sources. Current methods are expensive, and there is a lot of interest in looking for new materials for this task. One approach is to use porous crystalline materials, with a lot of interest in hybrid metal-organic materials that form crystal structures that contain large pores and channels. The project is to evaluate computer simulation methods currently being used within the scientific community. There has recently been an explosion of publications reporting on a wide range of simulation methodologies. For example, many methods use simple functions to describe the forces between atoms, which are parameterised either using quantum mechanical methods or by fitting to experimental data. One question to ask is how good are these methods, and are some approaches better than others? And also, it would be useful to evaluate the extent to which computer simulation actually makes a valid contribution. Are we better placed to design materials for CO2 capture based on simulation studies?

The atomic structure of nanoparticles
Nanoparticles are of great importance and interest for a wide variety of applications, from energy to healthcare. But what do we really know about their atomic structure? There are methods that can provide this information (for example, some diffraction and spectroscopy methods). But how good are these, and do they rely too much on what we know about the crystal structure of the bulk material? This project will review recent literature on this problem to better understand the state of knowledge of the atom structure of nanoparticles.

School of Physics and Astronomy

Prof. Martin Dove Project Abstracts