Spin-crossover is a high-spin-to-low-spin transition at a transition metal centre, induced by temperature or pressure. It is common in iron chemistry, but also occurs in some compounds of other common metals. Spin-crossover switching changes the volume, hardness and magnetic properties of the sample, and may also affect its colour, electrical resistance or other properties depending on the material. These properties have been harnessed in materials applications such as thermochromic inks; stimuli-responsive polymers; and solid state refrigeration.
Different materials can undergo spin-crossover abruptly or gradually with temperature, and with or without thermal hysteresis. This is governed by how strongly the individual switching centres in the material interact with each other, which in turn relates to its crystal packing. Designing a spin-crossover material with bespoke properties for a specific application is a challenging problem, which hinges on the structure, dynamics and cohesive forces within a crystal lattice.
This project will address part of this question, by correlating the switching characteristics of spin-crossover materials with their internal lattice vibrations. The student will use Leeds’ Advanced Research computing to perform electronic structure calculations of these materials using solid-state density functional theory (DFT) codes such as CASTEP, VASP and CP2K to probe and understand the vibrational and electronic properties of these materials. These calculations will be used to aid the interpretation of a range of experimental data including X-ray crystallography and powder diffraction; solid state magnetic and optical measurements; and infrared, Raman, Terahertz (THz) and neutron vibrational spectroscopy.
One particular focus of the work is to identify collective lattice vibrations correlating with abrupt spin-crossover switching in these materials, this information will then be used to rationally design new materials to enhance the appropriate lattice dynamics and increase the cooperativity of their switching properties to confirm the validity of that structure:function relationship.
This project will involve performing DFT calculations on a range of high performance hardware, processing of experimental data from a range of physical techniques as appropriate and the continued development of a number of post-processing software tools (i.e. PDielec). As such a relevant degree in Chemistry, Physics or equivalent with some experience in programming i.e. Python is essential to the role.
The projected start date is October 1st, although a later start date may also be possible.
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