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Welcome to the homepage of Dr. Nick Besley

Welcome!

I am an Associate Professor in Theoretical Chemistry here at the University of Nottingham. My group is interested in developing and applying quantum chemical methods to study a wide range of problems. For more information on my Research, see the "Research" sections.

I would welcome applications (from UK or EU) from students interested in a PhD position in my group.


Latest paper:

Relationship between X-Ray Emission and Absorption Spectroscopy and the Local H-bond Environment in Water

Iurii Zhovtobriukh, Nicholas A. Besley, Thomas Fransson, Anders Nilsson and Lars G.M. Pettersson published in the Journal of Chemical Physics

The connection between specific spectrum features in the water X-ray absorption (XAS) and X-ray emission (XES) spectra and the local H-bond coordination is studied based on structures obtained from path-integral molecular dynamics simulations using either the opt-PBE-vdW density functional or the MB-pol force field. Computing the XES spectrum using all molecules in a snapshot results in only one peak in the lone-pair (1b1) region while the experiment shows two peaks separated by 0.8- 0.9 eV. Different H-bond configurations were classified based on the local structure index (LSI) and a geometrical H-bond cone criterion. We find that tetrahedrally coordinated molecules characterized by high LSI values and two strong donated and two strong accepted H-bonds contribute to the low energy 1b1 emission peak and to the post-edge region in absorption. Molecules with asymmetric Hbond environment with one strong accepted and one strong donated H-bond and low LSI values give rise to the high energy 1b1 peak in the emission spectrum and mainly contribute to the pre-edge and main-edge in the absorption spectrum. The 1b1 peak splitting can be increased to 0.62 eV by imposing constraints on the H-bond length, i.e. for very tetrahedral structures short H-bonds (less than 2.68 Å) and for very asymmetric structures elongated H-bonds (longer than 2.8 Å). Such structures are present, but underrepresented, in the simulations which give more of an average of the two extremes.

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