Per Hyldgaard Research

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Our research group, Materials Physics and carbon engineering, performs theoretical-physics work in the BioNano Systems Laboratory at the Department of Microtechnology and NanoScience, MC2.

The research group is involved in a number of international collaborations, with the research groups of professors


Participation in the vdW-DF program

The group participates in a long-standing Rutgers-Chalmers collaboration, the vdW-DF program on extending DFT calculations to the broad class of sparse matter by formulation of a density functional with accounts of dispersive and/or van der Waals (vdW) interactions. Together with the reserach groups of Professors Elsebeth Schröder (also at MC2), Bengt I. Lundqvist (Chalmers and DTU, Denmark), and David C. Langreth (who sadly passed away in may 2011), we have worked and are working to develop, implement, test, and apply the new van der Waals density functional (vdW-DF) method.

A very large class of materials, like macro- and supra-molecular systems, have an electron distibution which, until recently have prevented accurate predictive descriptions. The class of systems are sparse materials as they contains important regions with a low or vanishing electron density where dispersive or vdW interactions contributes significantly. A predictive accounts requires quantum many-body calculations (QMBC) and efficientcy demands a formulation in terms of DFT. However, traditional state-of-the-art implementations of DFT invoke a semi-local description of the electron correlations and traditional state-of-the-art implementations fail for sparse materials where it is imperative to retain accounts of truly nonlocal correlations.

In the vdW-DF program we have been key contributors to the successfull development of a new density functional, called vdW-DF, which is fully nonlocal, which avoids double counting, and which provides simultaneous (and consistent) accounts of both dispersive or van der Waals interactions and of covalent, ionic, hydrogen and most metallic bonding. The method is proven highly efficient for molecules as well as for extended systems and provides what appears to be a first transferable (and parameter-free) account of both hard materials and sparse matter, for example, soft and supramolecular systems. The method has recieved significant international recognition.

Ab initio accounts of surfaces processes, growth, and interacting nonequilibrium transport

The group participates in several national international collaborations on modeling CVD oxide growth as well as atomic and molecular adsorption and diffusion on surfaces.

The group leader has also developed a Lippmann-Schwinger collision density functional theory (LSCDFT) which provides an, in principle, exact description of nonequilibrium tunneling in the presence of full (electron-electron) interaction. While usual DFT rest on a ground-state variational property but the new theory invokes variational properties of charge transfer rates.

Participation in the Chalmers eScience initiative.

It is very natural for our research group to seek to benefit from developments in eScience and we are proud of our participation in the Chalmers eScience initiative. The Pi have thus served as responsible author for both a Chalmers evaluation of the eScience interest and for the subsequent, successful application for the 2010 creation of the new Chalmers eScience center.

Our ongoing work to optimize vdW-DF implementations and to apply vdW-DF calculations to determine structure and the nature of binding (recognition) in crystals of smaller organic molecules has support from Vetenskapsrådet (VR). Ongoing work to model the nonequilibrium transport and current-induced excitation in quantum-cascade lasers has VINNOVA support. Building from (VR+VINNOVA) support and vdW-DF research investments, it is very natural for our research group to continue to extend the use of advanced computation and modeling and to develop accurate descriptions of materials behavior in a broader class of systems. We believe that we have a possibility to provide QMBC progress by extending the power of DFT calculations from hard materials to sparse matter and to molecular-recognition details in simple life processes.

We find it important combine physics insight with advanced computational thinking. We find it essential to not only use computational resources but to learn new theoretical frameworks to exploit the computation for improving physics insight. This applies to ongoing DFT work on structure in ultra-thin film oxide nucleation and to vdW-DF work on molecular systems. We find that our general research and the vdW-DF focus in particular defines interesting eScience challenges.

Revised Jan. 19, 2014 by Per Hyldgaard