LORBIT

LORBIT is a tag used in the Vienna Ab initio Simulation Package (VASP) to control the projection of Kohn–Sham wavefunctions onto localized atomic orbitals. It enables orbital-resolved analyses by decomposing electronic states into angular momentum channels associated with each atom, supporting quantities such as projected density of states (PDOS) and orbital character of bands. This makes LORBIT a key parameter for chemical bonding analysis and for understanding how different atoms and orbitals contribute to electronic structure.

When LORBIT is set to a non-zero value, VASP outputs orbital-projected information, typically in a file such as PROCAR. The PROCAR file contains the contributions of specified atomic orbitals (for example s, p, d, and sometimes f) to each k-point and band, allowing detailed visualization of orbital character across the band structure and energy spectrum. The exact set of projected orbitals and the format of the output depend on the chosen LORBIT value and the underlying pseudopotential or projector-augmented wave (PAW) setup. In general, higher LORBIT values yield more detailed projections but increase computational overhead and data size.

Practically, researchers use LORBIT to analyze the orbital origins of states near the Fermi level, to assign bonding character, and to interpret DOS and band structures in terms of specific atomic orbitals. The interpretation of LORBIT outputs can vary with the chosen potential, so users should consult the VASP manual and the documentation for their pseudopotentials to understand the precise meaning of each value and the corresponding output.