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 beyond.
QCDFT is a multiscale approach that is based entirely on density functional theory and allows quantum simulations at the large system. 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.
QCDFT 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 QCDFT.
On the other hand, although QCDFT 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 QCDFT is entirely based on DFT. This is an important feature and advantage of QCDFT, which qualifies it as a bona fide quantum simulation method.