| Autor: |
Mazzone, D. G., Gerber, S., Gavilano, J. L., Sibille, R., Medarde, M., Delley, B., Ramakrishnan, M., Neugebauer, M., Regnault, L. P., Chernyshov, D., Piovano, A., Fernandez-Diaz, T. M., Keller, L., Cervellino, A., Pomjakushina, E., Conder, K., Kenzelmann, M. |
| Rok vydání: |
2015 |
| Předmět: |
|
| Zdroj: |
Phys. Rev. B 92, 024101 (2015) |
| Druh dokumentu: |
Working Paper |
| DOI: |
10.1103/PhysRevB.92.024101 |
| Popis: |
We investigated the crystal structure and lattice excitations of the ternary intermetallic stannide Ca3Ir4Sn13 using neutron and x-ray scattering techniques. For T > T* ~ 38 K the x-ray diffraction data can be satisfactorily refined using the space group Pm-3n. Below T* the crystal structure is modulated with a propagation vector of q = (1/2, 1/2, 0). This may arise from a merohedral twinning in which three tetragonal domains overlap to mimic a higher symmetry, or from a doubling of the cubic unit cell. Neutron diffraction and neutron spectroscopy results show that the structural transition at T* is of a second-order, and that it is well described by mean-field theory. Inelastic neutron scattering data point towards a displacive structural transition at T* arising from the softening of a low-energy phonon mode with an energy gap of Delta(120 K) = 1.05 meV. Using density functional theory the soft phonon mode is identified as a 'breathing' mode of the Sn12 icosahedra and is consistent with the thermal ellipsoids of the Sn2 atoms found by single crystal diffraction data. |
| Databáze: |
arXiv |
| Externí odkaz: |
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