The Physical Sciences Colloquia are intended for a broad audience – from undergraduate students to retired professors. The topics encompass the interests of all research groups in the School: from Applied Optics, through Astrophysics, Planetary Science and Forensic Imaging to Functional Materials Physics and Chemistry.
The colloquia are held on Wednesdays at 2 pm in the Ingram Lecture Theatre (ILT) unless otherwise specified. The programme is constantly updated. Click on the speaker’s name and the talk’s title for biographical information/contact details and an abstract, respectively.
Everybody welcome!

Present Term

All our colloquia for this term will be on our Events Calendar which we regularly update when we have a confirmed speaker so make sure to check back regularly! You can also have a look at speakers for our present term by clicking on their entry below:

8th May 2019  – Ashley King, Natural History Museum, London

Title: TBC
Abstract: TBC


15th May 2019  – Nikitas Gidopoulos, University of Durham

Title: Accurate treatment of exchange vs self-interaction corrections in the Kohn-Sham equations

NB: Please note this event will take place in Ingram Building Room 110 at 1pm. 

Abstract: After a brief introduction to Kohn-Sham (KS) Density-Functional Theory (DFT), I shall present our Wave Function based approach [1] where an appropriate energy difference, which is a functional of an effective single-particle potential v(r), yields at its minimum the KS potential of DFT without any constraints on the electron density. Combined with a first-order expansion of the weakly interacting wave-function, our theory leads to new approximations for the XC potential. [1,2] At the exchange-only level, this theory leads to accurate exchange-only local potentials. The “exchange optimised effective potential” or exchange-only “exact exchange potential” of DFT is re-derived from a different point of view, as well as the “local Fock exchange” (LFX) potential, i.e., the local potential with the Hartree-Fock (HF) density. The two local potentials have been implemented in the plane wave code CASTEP and give remarkably similar band-structures [3,4]. For simple metals, the LFX potential, although based on a HF calculation, gives band-structures almost indistinguishable from those obtained from the local density approximation in DFT [5].

The accurate treatment of exchange implies the results are not contaminated with errors from self interactions (SIs). We have also tried to correct for the effects of SI errors in the effective KS potential directly, initially without changing the total energy, by imposing constraints in the minimisation of the total energy in popular approximate density functionals. These constraints affect the total energy only minimally but improve significantly the quality of the KS eigenvalues [6,7]. A hybrid scheme with 50% SI-corrected local potential and 50% nonlocal Fock exchange yields good ionisation energies for all the occupied orbitals, including from the core, managing to capture the enormous relaxation energy of the molecule when a core electron is ionised. Finally, an improvement of our constrained minimisation method makes it applicable to solids.

[1] N.I. Gidopoulos, Phys. Rev. A 83 040502 (2011).
[2] T. Callow, N.I. Gidopoulos, Eur. Phys. J. B, 91, 209 (2018).
[3] T.W. Hollins, S.J. Clark, K. Refson, N.I. Gidopoulos, Phys. Rev. B 85 235126 (2012).
[4] T.W. Hollins, S.J. Clark, K. Refson, N.I. Gidopoulos, J. Phys.: Condens. Matter 29, 04LT01 (2017).
[5] S.J. Clark, T.W. Hollins, K. Refson, N.I. Gidopoulos, J. Phys.: Condens. Matter 29, 374002 (2017).
[6] N.I. Gidopoulos, N.N. Lathiotakis, J. Chem. Phys. 136, 224109 (2012).
[7] T. Pitts, N.I. Gidopoulos, and N.N. Lathiotakis, Eur. Phys. J. B, 91, 130 (2018).


29th May 2019  – Dr Chunhui Li, University of Dundee

Functional Optical Coherence Tomography (OCT) development and application – Elastography and Angiography

Abstract: Optical Coherence Elastography (OCE) and Optical Coherence Angiography (OCTA) are the functional extension of traditional gray-level OCT structural images, which can provide more biomarkers to improve diagnostic accuracy. In this talk, recent study at Dundee on functional OCT development and application are presented. In OCE study, we confirmed a high diagnostic accuracy of OCE imaging in the detection and characterisation of prostate cancer for a large set of biopsy tissues obtained from men suspected to have prostate cancer using transrectal ultrasound (TRUS). The results showed that stiffness of cancer tissue was approximately 57.63% higher than that of benign tissue (Young’s modulus of 698.43 ± 125.29 kPa for cancerous tissue versus 443.07 ± 88.95 kPa for benign tissue with OCE. Using histology as a reference standard and 600kPa as a cut-off threshold, the data analysis showed sensitivity and specificity of 89.6% and 99.8% respectively. Corresponding positive and negative predictive values were 99.5% and 94.6% respectively. In OCTA study, we recently demonstrated our newly build flexible OCTA probe and its preliminary results in normal and cyst skin. These new findings suggest that functional OCT are increasingly important in advancing optical imaging system for diagnosis and therapy monitoring.

Past speakers are on the next page.

14th June 2019 – Dr Graham Newton, University of Nottingham

Title: The electronic properties of hybrid molecular metal oxides

NB: Please note this event will take place in Ingram Lecture Theatre at 2pm.

Molecular metal oxides or polyoxometalates (POMs) are characterised in large part by their rich redox and photo-chemistry, leading to applications in catalysis, nano-scale electronics and magnetism. They can be organofunctionalised to form organic-inorganic hybrid systems with new synergic properties.

Our group recently showed how the electronic structure and photo-catalytic performance of organic-inorganic hybrid POMs can be tuned through simple manipulation of the appended organic moieties.1 Here, recent findings on the tuneable redox properties, photochemistry and supramolecular assembly of hybrid molecular metal oxides will be discussed with particular focus on their application as additives in new functional materials.

SPS Colloquium - Dr Graham Newton

Figure 1: Substituent effects on the effective HOMO-LUMO gaps of organic-inorganic hybrid POMs.

 

1 a) J. M. Cameron, S. Fujimoto, K. Kastner, R. J. Wei, D. Robinson, V. Sans, G. N. Newton, H. Oshio, Chem. Eur. J. 2017, 23, 47-50; b) K. Kastner, A. J. Kibler, E. Karjalainen, J. A. Fernandes, V. Sans, G. N. Newton, J. Mater. Chem. A 2017, 5, 11577-11581; c) D. J. Wales, Q. Cao, K. Kastner, E. Karjalainen, G. N. Newton, V. Sans, Adv. Mater. 2018, 30 26.