Angelos Michaelides
Research Interests Our research aims at understanding important phenomena in surface- materials- and nano-science. Using concepts from quantum mechanics and statistical mechanics, we apply and develop methods and computer simulations to study processes of relevance to catalysis - such as the properties of metal surfaces and chemical reactions at surfaces - and processes of environmental relevance - such as the nucleation of ice or the dissolution of salts. Water and ice are major focuses of our work. Recent Publications
Abstract: Density-functional theory (DFT) and second order Moller-Plesset perturbation theory (MP2) calculations indicate that halogen atoms bond preferentially to halide substrate atoms on a series of alkali halide surfaces, rather than to the alkali atoms as might anticipated. Analysis of the electronic structures in each system reveals that this novel adsorption mode is stabilized by the formation of textbook two-center three-electron covalent bonds. The implications of these findings to, for example, nanostructure crystal growth are briefly discussed.
The ability of several density-functional theory (DFT) exchange-correlation functionals to describe hydrogen bonds in small water clusters (dimer to pentamer) in their global minimum energy structures is evaluated with reference to second order Moller-Plesset perturbation theory (MP2). Errors from basis set incompleteness have been minimized in both the MP2 reference data and the DFT calculations, thus enabling a consistent systematic evaluation of the true performance of the tested functionals. Among all the functionals considered, the hybrid X3LYP and PBE0 functionals offer the best performance and among the non-hybrid GGA functionals mPWLYP and PBE1W perform the best. The popular BLYP and B3LYP functionals consistently underbind and PBE and PW91 display rather variable performance with cluster size.
The long-standing belief that kaolinite is one of the most efficient natural ice nucleating agents because it provides a close lattice match Biography
A recent highlight of our work in the area of water-metal interfaces was the identification and characterization of the so-called “smallest particle of ice”: the water hexamer. In this project the cyclic water hexamer and a family of hydrated hexamer-like intermediates, were observed with scanning tunneling microscopy by Karina Morgenstern at the University of Hannover and characterized by us with density functional theory. The experimental STM image and the structure of the adsorbed hexamer predicted by theory are given below. In addition to the characterization of the water hexamers we also learned something new about the nature of interfacial hydrogen bonds: specifically we identified a hitherto unknown competition between the ability of water molecules to simultaneously form water-metal bonds and to accept H bonds. A. Michaelides and K. Morgenstern, Nature Mater. 6, 597 (2007) [associated press release]
The “smallest particle of ice” – a water hexamer as seen by STM (left) and quantum mechanics (right) |
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