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Most of the "first principles" simulations we do are with a theory known as density-functional theory (DFT). In principle it is exact but in practice it relies on an approximation for how electrons interact with each other. We are tackling the issue of the accuracy of DFT through extensive series of studies of small gas phase complexes, molecular crystals, and molecules at solid interfaces. These benchmark studies with techniques such as quantum Monte Carlo and coupled cluster come with extreme computational burdens. However, these benchmarks are essential to establish the accuracy of more traditional methods such as DFT, and help to ensure that the numbers we produce stand the test of time and experiment.

A major challenge for DFT is the accurate description of van der Waals interactions, and London dispersion in particular. London dispersion interactions are ubiquitous in nature contributing to the binding of biomolecules such as DNA, molecular crystals, and adsorption of molecules on surfaces. Many schemes have been developed that allow dispersion to be accounted for within DFT in a more or less approximate manner. One of the most promising and rigorous method is the nonlocal van der Waals density functional (vdW-DF) proposed by Langreth and Lundqvist and co-workers (M. Dion et al., Phys. Rev. Lett. 92, 246401, 2004). We have been working on developing improved versions on the vdw-DF approach, and in particular have developed optB88-vdW, optPBE-vdW, and optB86b-vdW functionals.

Related Publications 

Interaction between water and carbon nanostructures: How good are current density functional approximations?
JG Brandenburg, A Zen, D Alfè, A Michaelides – The Journal of chemical physics (2019) 151, 164702
Properties of the water to boron nitride interaction: From zero to two dimensions with benchmark accuracy.
YS Al-Hamdani, M Rossi, D Alfè, T Tsatsoulis, B Ramberger, JG Brandenburg, A Zen, G Kresse, A Grüneis, A Tkatchenko, A Michaelides – J Chem Phys (2017) 147, 044710
Performance of van der Waals Corrected Functionals for Guest Adsorption in the M-2(dobdc) Metal-Organic Frameworks
B Vlaisavljevich, J Huck, Z Hulvey, K Lee, JA Mason, JB Neaton, JR Long, CM Brown, D Alfè, A Michaelides, B Smit – Journal of Physical Chemistry A (2017) 121, 4139
How strongly do hydrogen and water molecules stick to carbon nanomaterials?
YS Al-Hamdani, D Alfè, A Michaelides – Journal of Chemical Physics (2017) 146, 094701
Evidence for stable square ice from quantum Monte Carlo
J Chen, A Zen, JG Brandenburg, D Alfè, A Michaelides – Physical Review B (2016) 94, 220102
Toward Accurate Adsorption Energetics on Clay Surfaces
A Zen, LM Roch, SJ Cox, XL Hu, S Sorella, D Alfè, A Michaelides – J Phys Chem C Nanomater Interfaces (2016) 120, 26402
Perspective: How good is DFT for water?
MJ Gillan, D Alfè, A Michaelides – The Journal of chemical physics (2016) 144, 130901
Communication: Water on hexagonal boron nitride from diffusion Monte Carlo.
YS Al-Hamdani, M Ma, D Alfè, OA von Lilienfeld, A Michaelides – Journal of Chemical Physics (2015) 142, 181101
Water on BN doped benzene: A hard test for exchange-correlation functionals and the impact of exact exchange on weak binding
YS Al-Hamdani, D Alfè, OA von Lilienfeld, A Michaelides – J Chem Phys (2014) 141, 18c530
On the accuracy of van der Waals inclusive density-functional theory exchange-correlation functionals for ice at ambient and high pressures.
B Santra, J Klimes, A Tkatchenko, D Alfè, B Slater, A Michaelides, R Car, M Scheffler – The Journal of chemical physics (2013) 139, 154702
Perspective: Advances and challenges in treating van der Waals dispersion forces in density functional theory.
J Klimeš, A Michaelides – J Chem Phys (2012) 137, 120901
Van der Waals density functionals applied to solids
J Klime, DR Bowler, A Michaelides – Physical Review B (2011) 83, 195131