QCDFT -- Quasi-continuum Density Functional Theory


Quasi-continuum Density Functional Theory is the first full quantum mechanics simulation of a system at the micron scale and a ground-breaking progress in computational mechanics of materials. This method was first developed by Q. Peng and his collaborators (PRB 78,054118,2008). QDFT is a multiscale approach that is based entirely on density functional theory and allows quantum simulations at the micron scale and beyond. This method combines the coarse graining idea of the adaptive finite element method and the coupling strategy of the quantum mechanics/molecular mechanics (QM/MM) method, and represents a major advance in the quantum simulation of materials properties. It should be stated at the outset that QDFT is not a brute-force electronic structure method, but rather a multiscale approach that can treat large systems - effectively up to billions of electrons. Therefore, some of the electronic degrees of freedom are reduced to continuum degrees of freedom in QDFT. On the other hand, although QDFT utilizes the idea of QM/MM coupling, it does not involve any classical/empirical potentials (or force fields) in the formulation - the energy calculation of QDFT is entirely based on DFT. This is an important feature and advantage of QDFT, which qualifies it as a bona fide quantum simulation method. The method was verified by a multitude of tests, including nano- indentation of an Al thin film.

Simulation crack-tip in aluminum. Load and then relax. (click the picture to watch the movie)

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