What it can do

tetr is an interactive menu-driven program which enables you:

• can read in existing input files from VASP, SIESTA, old CASTEP, xyz format
• can save the current geometry in the same formats
• creates a geometry file from scratch, including from the space group symbol (both in 2D and 3D), or modifies an existing geometry in various ways
• builds a cluster from the bulk cell atomic positions; can terminate some or all of the cluster boundary atoms with H atoms;
• controls calculation of molecular or lattice vibrations taking into account irreducible representations of the system (either the point group or the group of internal translations within the supercell); in the case of a molecule, translations and rotations of the molecule as a whole are automatically eliminated; can do phonon DOS, animations of normal modes, recalculate the phonons for different isotops (keeping the same force constant matrix);
• creates $\mathbf{k}$-points for the ground state (Manchorst-Pack), DOS (the tetrahedral method with complete account of the point symmetry of the cell) or band-structure calculations (along a chosen line in the Brillouin zone);
• calculates the Coulomb (Ewald) potential at an arbitrary point in the cell in the point-ion approximation,
• some additional useful options designed to analyze the system geometry: compare with other geometry files, e.g. before and after relaxation; a calculator of interatomic distances; check a point in the cell for equivalence with existing atoms; save atomic positions within a box across adjacent unit cells
• Potential energy surface (PES): move atoms in the cell keeping the point symmetry: this is useful for calculating the PES for the ground state symmetry.