Category:Electronic ground-state properties: Difference between revisions

At the end of an electronic minimization, VASP obtained a converged set of orbitals. From the orbitals, we compute the corresponding density via k-point integration. The orbitals and the density reveal important insights into material properties and are often the first step towards analyzing and understanding a material.

Properties of orbitals

For practical purposes, one is most interested in the energy eigenvalue of the orbitals and their local projections. Consider first the eigenvalues: Counting all orbitals with eigenvalues in a certain energy interval yields the density of states (DOS). Often looking at the DOS can provide valuable insight into the electronic properties of a material and is therefore often the first step to start towards understanding a novel material. The band structure contains even more details about the electronic eigenvalues by resolving them with respect to the Block vector k. Usually, one uses high-symmetry paths in the Brillouin zone for band structures. They make it easy to recognize fundamental and direct bandgaps of the material. Alternatively, VASP reports these to the OUTCAR file with the verbosity controlled by the BANDGAP tag. The electronic eigenvalues determine the occupations of each orbital in conjunction with the settings for ISMEAR, SIGMA, and EFERMI.

Next, we consider the projections of the orbitals which you activate with the LORBIT tag. VASP projects each orbital onto functions with defined angular momentum near each ion. This site projection augments the data produced by DOS and band structure calculations. An easy way to visualize these projections is with py4vasp. In addition, the projections describe how much charge has a particular angular momentum and spin near an ion. This serves as a good approximation for the magnetic structure of the system.