Bilbao Crystallographic Server NEUTRON Help

NEUTRON - A program for computing phonon extinction rules of inelastic neutron scattering and thermal diffuse scattering experiments

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NEUTRON is a computer program for calculating the phonon extinction rules for inelastic neutron scattering experiments. Given the space group and the phonon symmetry specified by the wave vector q, the program examines the inelastic neutron scattering activity of the corresponding phonons for all possible types of scattering vectors Q=H-q, where H is a reciprocal lattice vector.

The applied algorithm is based on a recently proven theorem that demonstrates the existence of symmetry-based selection rules for the phonon activity in inelastic neutron scattering experiments: the resulting phonon absences depend only on the mode symmetry and the scattering vector Q, and not on the specific atomic positions of the crystal structures (Perez-Mato et al., 1998). Using the distribution of the reciprocal lattice vectors (Brillouin zones) into types with respect to the symmetry group of the scattering vector, it is possible to show that Brillouin zones belonging to the same type are characterized by the same set of selection rules. The derived extinction rules prove to be very useful for the identification of the symmetries of the measured phonons, and their systematic use helps the optimization of inelastic neutron scattering experiments (Aroyo et al., 2002a). These selection rules also apply to phonon X-ray inelastic scattering, and their use has been successfully extended to thermal diffuse scattering studies (Aroyo et al., 2002b).

For more details related to the program NEUTRON, its algorithm and the procedure for the calculation of the phonon selection rules, the user is referred to Kirov et al., 2003.


  1. Perez-Mato, J.M., Aroyo, M.I., Hlinka, J., Quilichini, M. & Currat, R. (1998). Phys. Rev. Lett. 81 2462-2465.
  2. Aroyo, M.I., Boysen, H. & Perez-Mato, J.M. (2002a). Physica B 316-317, 154-157.
  3. Aroyo, M.I., Boysen, H. & Perez-Mato, J.M. (2002b). Applied Physics A 74, S1043-S1045.
  4. Kirov, A.K., Aroyo, M.I. & Perez-Mato, J.M.(3003). J. Applied Crystallogr. (to appear).

Input Data

Output Data

The OUTPUT of the program consists of three main blocks: a Space-group data block, a q-vector data block including the little group irreducible representations (irreps), and a data-block with Q-vector types and extinction rules.

Examples and screenshots

Example 1: Phonon extinction rules for q=(0,0,0) with label GM, for the space group Pnma

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