The empty lattice approximation is a theoretical electronic band structure model in which the potential is periodic and weak (close to constant). One...

freely through the crystal lattice of a solid. The model is closely related to the more conceptual empty lattice approximation. The model enables understanding...

include the following: Empty lattice approximation: the "band structure" of a region of free space that has been divided into a lattice. k·p perturbation theory...

one end of the lattice, but if the energy is at the band edge, the state is delocalized across the lattice. Empty lattice approximation Nearly free electron...

The GW approximation (GWA) is an approximation made in order to calculate the self-energy of a many-body system of electrons. The approximation is that...

orbitals belong to different point-group representations. The reciprocal lattice and the Brillouin zone often belong to a different space group than the...

enough for calculations in quantum chemistry until the 1990s, when the approximations used in the theory were greatly refined to better model the exchange...

these approaches is to provide a reliable solution (or an accurate approximation) of the quantum many-body problem. The diverse flavors of quantum Monte...

continuation to the free electron model can be obtained by assuming the empty lattice approximation, which forms the basis of the band structure model known as the...

The muffin-tin approximation is a shape approximation of the potential well in a crystal lattice. It is most commonly employed in quantum mechanical simulations...

“bills” to pay, e.g., (1) the calculation of KKR structure constants, the empty lattice propagators, must be carried out by the Ewald's sums for each energy...

electron model Tight binding Muffin-tin approximation k·p perturbation theory Empty lattice approximation GW approximation Korringa–Kohn–Rostoker method v t...

equation and its set of solutions: For molecules, the Born–Oppenheimer approximation is inherently assumed. The true wavefunction should also be a function...

functions. The PAW method is typically combined with the frozen core approximation, in which the core states are assumed to be unaffected by the ion's...

solid, V is a periodic function, with the same periodicity as the crystal lattice. Bloch's theorem proves that the solutions to this differential equation...

chemistry methods are based on the Hartree–Fock formalism, but make many approximations and obtain some parameters from empirical data. They are very important...

electron model Tight binding Muffin-tin approximation k·p perturbation theory Empty lattice approximation GW approximation Korringa–Kohn–Rostoker method v t...

The model solid approximation is a method used for determining the extrema of energy bands in semiconductors. The method was first proposed for silicon-germanium...

all previous times. Consequently, the development of time-dependent approximations for the implementation of TDDFT is behind that of DFT, with applications...

orbitals – as linear combinations of atomic orbitals (LCAO). These approximations are made by applying the density functional theory (DFT) or Hartree–Fock...

includes the empty substructure in case the algebra A has no nullary operations. Then: The set Sub(A), ordered by set inclusion, is a lattice. The greatest...

the nonrelativistic Schrödinger equation within the Born–Oppenheimer approximation for a quantum chemical multi-electron system. Mathematically, configuration...

electron model Tight binding Muffin-tin approximation k·p perturbation theory Empty lattice approximation GW approximation Korringa–Kohn–Rostoker method v t...

within the Born–Oppenheimer approximation (although schemes have also been drawn up to work without the BO approximation). One possible improvement to...

physics and chemistry, the Hartree–Fock (HF) method is a method of approximation for the determination of the wave function and the energy of a quantum...

In chemistry, the lattice energy is the energy change (released) upon formation of one mole of a crystalline compound from its infinitely separated constituents...

practice, instead of deriving approximations for interacting kinetic energy, much effort was devoted to deriving approximations for non-interacting (Kohn–Sham)...

correct only in the limit of an infinite nuclear charge. Using the approximation for realistic systems yields poor quantitative predictions, even failing...

consists of a lattice of atoms, each with an outer shell of electrons that freely dissociate from their parent atoms and travel through the lattice. This is...

electronic Schrödinger equation is obtained within the Born–Oppenheimer approximation [ T ^ + v ^ ext + V ^ ee ] Ψ 0 = E 0 Ψ 0 {\displaystyle [{\hat {T}}+{\hat...