gammapt

Gammapt is a shorthand term used in computational physics and crystallography to denote the gamma point, the k = 0 point at the center of the first Brillouin zone in reciprocal space. The gamma point is a high-symmetry point where the wavevector vanishes, and properties calculated at this point reflect zone-center physics such as optical transitions and long-wavelength phonons.

In practice, gammapt appears in tutorials, scripts, and input files as a label for calculations performed at k = 0, or as a variable representing this point in k-point sampling schemes. Many software packages that perform electronic structure or lattice dynamics calculations allow explicit specification of k-points; gammapt corresponds to the single point with coordinates (0,0,0) (in reduced coordinates) or the point labeled Gamma. It’s often used as a starting point for band-structure calculations or as a reference against which other k-points are compared. However, while important, gamma-point data do not capture the full dispersion of bands or phonons across the Brillouin zone; a full analysis typically requires sampling a grid of k-points.

The term gammapt is informal shorthand rather than a formal nomenclature in the scientific literature. It may appear in code comments, tutorials, or user forums, and is not universally adopted across all codes. In peer-reviewed articles, the gamma point is usually written as “Gamma point” or described by its k-vector coordinates.

See also: gamma point; Brillouin zone; k-point sampling; reciprocal lattice; density functional theory; phonons.