K-Point Sampling

For periodic systems (crystals, surfaces), the electronic wavefunctions must be sampled at discrete points in the reciprocal space, known as k-points. A denser sampling grid leads to higher accuracy but significantly increases computational cost.

• k-grid Cutoff: The simplest method. You provide a real-space cutoff distance (in Angstroms), and Siesta automatically generates a commensurate k-point grid. Larger values result in sparser grids.
• Monkhorst-Pack Grid: Provides direct control. You specify the number of k-points to sample along each reciprocal lattice vector (e.g., 4x4x4 for a bulk crystal).