Phonon dispersion curves were calculated theoretically. A small value of C12 was explained in terms of a volume-dependent force acting on La atoms. The calculated phonon dispersion curves were in good agreement with measured ones.

Lattice Dynamics in LaB6 and YbB6. Takegahara, K., Kasaya, M., Goto, T., Kasuya, T.: Physica B+C, 1985, 130[1-3], 49-51. See also: Solid State Communications, 1985, 53[1], 15-9